TAHMOOR COLLIERY
LONGWALL 24A
END OF PANEL
SUBSIDENCE MONITORING REPORT
FOR LONGWALL 24A
AT TAHMOOR COLLIERY
Mine Subsidence Engineering Consultants
Level 1, 228 Victoria Avenue - Chatswood – NSW 2103 PO Box 3047 – Willoughby North – NSW 2068
Tel. (02) 9413 3777 Fax. (02) 9413 3822 Email: [email protected]
www.minesubsidence.com
REPORT NO. MSEC335
January 2009
Mine Subsidence Engineering Consultants Xstrata Coal Tahmoor Colliery Report No. MSEC335 Longwall 24A January 2009 End of Panel Report Subsidence Monitoring Report
i
DOCUMENT REGISTER
Revision Description Author Checker Date
01 MJ DJK
Report produced for:-
Compliance with conditions attached to the SMP Approval by the Department of Primary Industries for Longwall 24A – 0m to 250m and Longwall 24A – 250m to End.
Acknowledgments
We would like to acknowledge the extensive contribution provided by various organisations to this report. These organisations have conducted most of the on-ground surveys and inspections. We would particularly like to acknowledge the close dialogue between Tahmoor Colliery and the Mine Subsidence Board, which has ensured a timely and accurate flow of information regarding impacts to structures.
We would like to acknowledge the following organisations:
Australian Rail Track Corporation
Department of Primary Industries
Geoterra
Hydrometric Consulting Services
Lean & Hayward Surveyors
Lutibo (Colin Dove)
Meadows Consulting
Mine Subsidence Board
Pidgeon Civil Engineering
Sunrise Building and Property Services
Sydney Water
Tahmoor Colliery
References
Mine Subsidence Engineering Consultants, (2004). Tahmoor Colliery Longwalls 24 to 26 Report on the Prediction of Subsidence Parameters and the Assessment of Subsidence Impacts on Surface and Sub-Surface Features due to Mining Longwalls 24 to 26 at Tahmoor Colliery in support of an SMP Application. Volume 1. Report No. MSEC157, Revision C, March 2006.
Geoterra, (2008). Xstrata Coal – Tahmoor Colliery End of Longwall 24A Surface Water, Dams & Groundwater Monitoring Report, Tahmoor NSW. GeoTerra Report No. TA8-R2, January 2009.
John Matheson & Associates Pty Ltd, August 2008. Tahmoor Town Centre - Report on column cracking at base of concrete columns in basement car park.
Pells Sullivan Meynink Pty Ltd, May 2008. Letter report entitled Assessment of Recent Rockfalls in the Bargo Gorge.
Mine Subsidence Engineering Consultants Xstrata Coal Tahmoor Colliery Report No. MSEC335 Longwall 24A January 2009 End of Panel Report Subsidence Monitoring Report
ii
TABLE OF CONTENTS
DOCUMENT REGISTER i
LIST OF DRAWINGS AND ILLUSTRATIONS iv
CHAPTER 1. INTRODUCTION 6
CHAPTER 2. COMPARISON BETWEEN OBSERVED AND PREDICTED SUBSIDENCE MOVEMENTS 7
2.1. Comparison between Predicted and Observed Systematic Subsidence Movements 8
2.2. Identification of Non-Systematic Subsidence Movements 11
2.3. Bargo River 13
2.3.1. Angle of Draw Surveys 15
2.4. Main Southern Railway 15
2.4.1. Strain Gauge and Switch Displacement Monitoring 15
2.4.2. Thirlmere Way Overbridge 16
2.4.3. Platform Clearance Surveys 16
2.5. Sewer Infrastructure 16
2.6. Power Pole Surveys 19
2.7. Tahmoor Town Centre 19
2.8. Inghams 19
2.8.1. Ground and Building Monitoring Results 19
2.8.2. Ammonia Pipes 19
2.8.3. Pipe Stress Transducers (PSTs) 20
2.8.4. Discussion 20
CHAPTER 3. SUMMARY OF SURVEYS AND INSPECTIONS 21
CHAPTER 4. IMPACTS TO SURFACE FEATURES 26
4.1. Summary of Impacts to Surface Features 26
4.2. Bargo River Gorge 29
4.2.1. Water Quality and Flow Impacts 29
4.2.2. Rockfalls 29
4.2.3. Exceedence of Defined Triggers 29
4.3. Main Southern Railway 29
4.3.1. Thirlmere Way Overbridge 30
4.3.2. Exceedence of Defined Triggers 30
4.4. Roads 30
4.4.1. Exceedence of Defined Triggers 30
4.5. Potable Water Infrastructure 32
4.5.1. Exceedence of Defined Triggers 32
4.6. Gas Infrastructure 32
Mine Subsidence Engineering Consultants Xstrata Coal Tahmoor Colliery Report No. MSEC335 Longwall 24A January 2009 End of Panel Report Subsidence Monitoring Report
iii
4.6.1. Exceedence of Defined Triggers 32
4.7. Sewer Infrastructure 32
4.7.1. Exceedence of Defined Triggers 32
4.8. Electrical Infrastructure 33
4.8.1. Exceedence of Defined Triggers 33
4.9. Telecommunication Infrastructure 33
4.9.1. Exceedence of Defined Triggers 33
4.10. Inghams Infrastructure 33
4.10.1. Processing Plant 33
4.10.2. Inghams Dams 34
4.10.3. Exceedence of Defined Triggers 34
4.11. Residential Structures and Public Amenities 34
4.11.1. Comparison in General 36
4.11.2. Comparison based on Predicted Impact Categories 37
4.11.3. Discussion of Results 37
4.11.4. Swimming Pools 42
4.11.5. Associated Structures 42
4.11.6. Fences 42
4.11.7. Exceedence of Defined Triggers 42
4.12. Public Amenities 42
4.12.1. Exceedence of Defined Triggers 42
4.13. Tahmoor Town Centre 42
4.13.1. Observations of Cracking 42
4.13.2. Possible Causes of Cracking 39
4.13.3. Conclusions 39
4.13.4. Exceedence of Defined Triggers 39
CHAPTER 5. SUMMARY OF RESULTS 44
Mine Subsidence Engineering Consultants Xstrata Coal Tahmoor Colliery Report No. MSEC335 Longwall 24A January 2009 End of Panel Report Subsidence Monitoring Report
iv
LIST OF DRAWINGS AND ILLUSTRATIONS
Drawings
Drawing No. Description
MSEC335-01 Longwall 24A Monitoring Lines
MSEC335-02 Longwall 24A Impacts
Figures
Figure No. Description
MSEC335-01 Total Subsidence Profiles along Bradbury Street Line
MSEC335-02 Total Subsidence Profiles along BC Line
MSEC335-03 Total Subsidence Profiles along Castlereagh Street Line
MSEC335-04 Total Subsidence Profiles along Chapman Street Line
MSEC335-05 Total Subsidence Profiles along Courtland Avenue Line
MSEC335-06 Total Subsidence Profiles along Emmett Street Line
MSEC335-07 Total Subsidence Profiles along Larkin Street Line
MSEC335-08 Total Subsidence Profiles along Lintina Street Line
MSEC335-09 Total Subsidence Profiles along LW24A Draw Line
MSEC335-10 Total Subsidence Profiles along LW25 Draw Line
MSEC335-11 Total Subsidence Profiles along LW26 Draw Line
MSEC335-12 Total Subsidence Profiles along the Main Southern Railway Corridor Line
MSEC335-13 Incremental Subsidence Profiles the Main Southern Railway Corridor Line
MSEC335-14 Total Subsidence Profiles along Mitchell Close Line
MSEC335-15 Total Subsidence Profiles along Pandora Place Line
MSEC335-16 Total Subsidence Profiles along Progress Street Line
MSEC335-17 Incremental Subsidence Profiles along Progress Street Line
MSEC335-18 Total Subsidence Profiles along Ralfe Street Line
MSEC335-19 Total Subsidence Profiles along Remembrance Drive Line
MSEC335-20 Incremental Subsidence Profiles along Remembrance Drive Line
MSEC335-21 Total Subsidence Profiles along Remembrance Drive Shopfronts Line
MSEC335-22 Total Subsidence Profiles along Tanya Place Line
MSEC335-23 Total Subsidence Profiles along Thirlmere Way Line
MSEC335-24 Incremental Subsidence Profiles along Thirlmere Way Line
MSEC335-25 Total Subsidence Profiles along Inghams Dam Line
MSEC335-26 Total Subsidence Profiles along Inghams East-West Line
MSEC335-27 Total Subsidence Profiles along Inghams High-Rise Freezer Line
MSEC335-28 Total Subsidence Profiles along Inghams North-South Line
MSEC335-29 Total Subsidence Profiles along Inghams Pipe Support Line (PS1-PS15)
MSEC335-30 Total Subsidence Profiles along Inghams Pipe Support Line (PS16-PS23)
Mine Subsidence Engineering Consultants Xstrata Coal Tahmoor Colliery Report No. MSEC335 Longwall 24A January 2009 End of Panel Report Subsidence Monitoring Report
v
MSEC335-31 Total Subsidence Profiles along Inghams Plant Line
MSEC335-32 Total Subsidence Profiles along Mermaid Pool Line
MSEC335-33 Total Subsidence Profiles along Bargo River X1 Line
MSEC335-34 Total Subsidence Profiles along Bargo River X2 Line
MSEC335-35 Total Subsidence Profiles along Bargo River X3 Line
MSEC335-36 Total Subsidence Profiles along Bargo River X3a Line
MSEC335-37 Total Subsidence Profiles along Bargo River X4 Line
MSEC335-38 Total Subsidence Profiles along Bargo River X5a Line
MSEC335-39 Total Subsidence Profiles along Bargo River X5b Line
MSEC335-40 Total Subsidence Profiles along Bargo River X5c Line
MSEC335-41 Total Subsidence Profiles along Bargo River X6 Line
Mine Subsidence Engineering Consultants 6 Xstrata Coal Tahmoor Colliery Report No. MSEC335 Longwall 24A January 2009 End of Panel Report Subsidence Monitoring Report
CHAPTER 1. INTRODUCTION
This report has been prepared by Mine Subsidence Engineering Consultants Pty Ltd (MSEC) for Xstrata Coal Tahmoor Colliery to comply with conditions of the SMP Approval by the Department of Primary Industries, particularly Clause 23.
This report includes:
A summary of the subsidence and environmental monitoring results for Longwall 24A; An analysis of these results against the relevant impact assessment criteria, monitoring results
from previous panels and predictions provided in the SMP; The identification of any trends in the monitoring results; A description of actions that were taken to ensure adequate management of any potential
subsidence impacts
The location of Longwall 24A is shown in Drawing No. MSEC335-01, which together with all other drawings, is attached in Appendix A at the back of this report.
This report also includes many of the movements and impacts observed during the extraction of Longwalls 22 to 24A. Note that Longwall 24B was extracted prior to Longwall 24A. The dates of extraction for all longwalls are provided in Table 1-1.
Table 1-1 Start and Finish Dates for Longwalls 22 to 24A
Longwall Start Date Completion Date
Longwall 22 31 May 2004 27 July 2005
Longwall 23A 13 September 2005 21 February 06
Longwall 23B 22 March 2006 26 August 2006
Longwall 24B 14 October 2006 02 October 2007
Longwall 24A 15 November 2007 19 July 2008
The predicted movements and impacts resulting from the extraction of Longwalls 24 to 26 were provided in Report No. MSEC157 (Revision C), which was issued in March 2006.
Longwall 24A was approximately 991 metres long and 283 metres wide, rib to rib. The pillar width was approximately 34.5 metres wide, rib to rib. However, there is a coal barrier between Longwall 24A and the previously extracted 200 Panels of approximately 160 metres width. The depth of cover was relatively consistent over the panel, varying between 430 and 440 metres. While the seam thickness was approximately 2.1 metres, Tahmoor Colliery advised that the design cut was 2.15 metres and the shearer would never cut below 2.05 metres.
Chapter 2 of this report describes the monitoring lines and monitoring points at Tahmoor Colliery, and provides comparisons between the observed and predicted movements resulting from the extraction of Longwall 24A.
Chapter 3 of this report summarises the surveys and inspections undertaken during the mining of Longwall 24A.
Chapter 4 of this report describes the reported impacts on surface features resulting from the extraction of Longwall 24A, and compares these with the predicted impacts. The reported impacts on surface water and ecology are provided in other reports.
Appendix A includes all drawings and figures associated with this report.
Mine Subsidence Engineering Consultants 7 Xstrata Coal Tahmoor Colliery Report No. MSEC335 Longwall 24A January 2009 End of Panel Report Subsidence Monitoring Report
CHAPTER 2. COMPARISON BETWEEN OBSERVED AND PREDICTED SUBSIDENCE MOVEMENTS
As set out in the Surface Safety and Serviceability Management Plan, for Tahmoor Colliery Longwalls 24 to 26, regular subsidence surveys have been conducted along monitoring lines that have been established in selected streets. The monitoring is being undertaken to compare observed movements against predicted movements, and to identify any anomalous movements that might potentially have an adverse effect on surface features. The locations of all of the monitoring lines near Longwall 24A are shown in Drawing No. MSEC335-01.
A number of these monitoring lines were installed prior to the commencement of Longwall 24A to measure subsidence movement at key surface features such as the Inghams Plant, Remembrance Drive and Main Southern Railway.
Additional monitoring lines were installed as mining progressed when it became apparent that the urban area may experience increased subsidence. Some subsidence had already developed at each of these additional survey marks prior to the initial survey. A summary of all monitoring lines, dates of initial survey and estimated subsidence prior to initial survey are provided in Table 2-1.
Table 2-1 Summary of Monitoring Lines directly above Longwall 24A
Monitoring Line Date of Initial
Survey Estimated subsidence due to LW 24A
prior to initial survey (mm)
LW24A Draw Line 15 November 2007 0
Dam Line 14 November 2007 0
East-West Line 14 November 2007 0
North-South Line 14 November 2007 0
High-Rise Freezer Line (HRF1 to HRF5)
14 November 2007 0
High-Rise Freezer Line (HRF6 to HRF18)
14 March 2008 30 to 130
Plant and Pipe Support Lines 04 December 2007 5
BC Line 22 April 2008 70 to 245
Ralfe Street Line 10 April 2008 20 to 25
Lintina Street Line 02 May 2008 25 to 70
Courtland Avenue Line 02 May 2008 15 to 55
Tanya Place Line 02 May 2008 30 to 50
Mitchell Close Line 02 May 2008 30 to 35
Pandora Place Line 02 May 2008 20 to 30
Progress Street Line 03 October 2006 0
Remembrance Drive Line 13 May 2005 0
Larkin Street Line 20 May 2008 10 to 30
York Street Line 20 May 2008 15 to 25
Emmett Street Line 20 May 2008 20 to 35
In addition to the monitoring lines, subsidence monitoring was conducted at survey stations located at and around the Tahmoor Town Centre, selected power poles and at the Bargo Gorge in accordance with the Surface Safety and Serviceability Management Plan.
Mine Subsidence Engineering Consultants 8 Xstrata Coal Tahmoor Colliery Report No. MSEC335 Longwall 24A January 2009 End of Panel Report Subsidence Monitoring Report
Surveys were undertaken at regular intervals during the extraction of Longwall 24A and the End of Panel surveys were conducted during July and August 2008. The observed total and incremental subsidence profiles along the monitoring lines are provided in Figs. MSEC335-01 to MSEC335-41.
2.1. Comparison between Predicted and Observed Systematic Subsidence Movements
Observed subsidence, tilt and curvature due to the mining of Longwall 24A have substantially exceeded predictions. Maximum observed subsidence was 1169 mm, which was more than double the maximum predicted subsidence of 509 mm. While observed tilts and curvature were also substantially greater than predicted, observed ground strains were within the normal range.
The observation of increased subsidence was not observed at other nearby longwalls at Tahmoor Colliery, where there was a reasonable correlation between predicted and observed profiles over Longwalls 22, 23 and 24B.
Observed subsidence was greatest above the southern half of Longwall 24A, and gradually reduced in magnitude towards the northern half of the longwall, which was directly beneath the urban area of Tahmoor. These observations are shown graphically in Figure 2.1, which shows observed subsidence at survey pegs located along the centreline of Longwall 24A.
Figure 2.1 Observed Subsidence along Centreline of Longwall 24A
It can be seen from Figure 2.1 that while observed subsidence was substantially greater than predicted above the commencing end of the longwall, observed subsidence compared reasonably well with predictions towards the finishing end of Longwall 24A.
-350 -250 -150 -50 50 150 250 350 450 550 650 750 850 950 1050 1150 1250 1350Distance from goaf edge (m)
LW 24A LW 24B120011001000
900800700600500400300200100
0
Sub
side
nce
(mm
)
Peg 24-155.1 x prediction
Peg 24-164.9 x prediction
Peg 24-174.2 x prediction
Peg 24-183.6 x prediction
Peg 24-193.1 x prediction
Peg HRF102.3 x prediction
Peg RF191.9 x prediction
Peg LA91.2 x prediction
Peg R151 x prediction
Peg L11 x prediction
Observed subsidence atsurvey pegs during LW 24A
Observed Subsidence alongCentreline at end of LW 24A
Predicted Subsidence due toLW 24A (MSEC157)
250
255
260
265
270
275
280
285
Sur
face
Lev
el A
HD
(m
)
LW 24A15
-Nov
-07
11-D
ec-0
7
14-J
an-0
8
25-J
an-0
8 to
28-
Mar
-08
14-A
pr-0
8
21-A
pr-0
8
28-A
pr-0
8
8-M
ay-0
8
12-M
ay-0
8
19-M
ay-0
8
26-M
ay-0
8
2-Ju
n-08
11-J
un-0
8 to
19-
Jul-0
8
24-1 2
4-2
24-
324
-4 24-5 24
-624
-72
4-8
24-9
24-1
02
4-11
24-1
224
-13
24-
1424
-15
24-1
624
-17
24-1
82
4-19
HR
F10
RF
19
LA9
R15
L1
Y1
94.3
2T
71
LW 24B
I:\Projects\Tahmoor\SurveyData\LW24A Draw Line\LW24A Draw Line (EOP).grf
Mine Subsidence Engineering Consultants 9 Xstrata Coal Tahmoor Colliery Report No. MSEC335 Longwall 24A January 2009 End of Panel Report Subsidence Monitoring Report
Maximum observed incremental and total subsidence parameters for all monitoring lines surveyed during Longwall 24A are summarised in Table 2-2. The maximum value for each parameter is highlighted.
Table 2-2 Summary of Maximum Subsidence along Monitoring Lines
Monitoring Line
Maximum Observed
Subsidence (mm)
Maximum Observed
Tilt (mm/m)
Maximum Observed Hogging
Curvature (km-1)
Maximum Observed Sagging
Curvature (km-1)
Maximum Observed
Tensile Strain
(mm/m)
Maximum Observed
CompressiveStrain
(mm/m)
Bradbury Street 47 0.8 0.05 -0.05 0.4 -0.3
BC Line 779 5.1 0.11 -0.18 0.1 -0.3
Castlereagh Street 17 0.2 0.01 -0.01 0.4 -0.2
Chapman Street 15 0.2 0.01 -0.01 0.2 -0.5
Courtland Avenue 730 6.0 0.14 -0.03 0.4 -0.6
Emmett Street 84 0.5 0.02 -0.01 0.1 -0.1
Larkin Street 110 1.2 0.03 -0.01 0.4 -0.2
Lintina Street 630 3.6 0.09 -0.13 0.1 -1.1
LW24A Draw Line 1091 10.2 0.15 -0.14 1.3 -0.4
LW25 Draw Line 12 0.3 0.01 -0.01 0.3 -0.3
LW26 Draw Line 20 0.4 0.02 -0.02 0.5 -0.5
Main Southern Railway
40 0.6 0.03 -0.06 0.3 -0.5
Mitchell Close 471 4.3 0.06 -0.23 0.3 -4.8
Pandora Place 120 1.1 0.02 -0.02 0.1 -0.1
Progress Street 26 0.3 0.08 -0.05 - -
Ralfe Street 937 8.4 0.1 -0.13 1.2 -3.2
Remembrance Drive 199 3.0 0.12 -0.11 0.8 -0.4
Remembrance Drive Shopfronts
127 1.4 0.10 -0.03 - -
Tanya Place 462 6.8 0.10 0.00 0.9 0.0
Thirlmere Way 36 1.5 0.12 -0.08 0.2 -0.2
Inghams
Dam Line 762 4.7 0.06 -0.14 0.5 -0.3
East-West Line 602 6.4 0.08 -0.03 1.0 -0.2
High-Rise Freezer Line
1169 12.7 0.29 -0.38 1.0 -2.5
North-South Line 174 0.5 0.01 -0.03 0.1 -0.2
Pipe Support Line 108 0.7 0.14 -0.10 0.7 -0.7
Plant Line 118 0.7 0.12 -0.08 2.8 -0.4
Mine Subsidence Engineering Consultants 10 Xstrata Coal Tahmoor Colliery Report No. MSEC335 Longwall 24A January 2009 End of Panel Report Subsidence Monitoring Report
The distribution of subsidence transverse to the longwalls is illustrated by the results along the High-Rise Freezer Line (Figure 2.2). This shows that subsidence on the tailgate side (Inghams side) was greater than the subsidence on the maingate side (Progress Street side). The potential for increased subsidence on the tailgate side was anticipated as the tailgate side is located above mostly solid, unmined coal reserves that lie between a previously mined area (200 Panels) and the currently mined Longwall 24A. Observations of increased subsidence have been experienced in similar previous mining situations.
0 50 100 150 200 250 300 350 400 450Distance along High-Rise Freezer Line from Survey Mark NS7 (m)
LW 24A
-14-12-10
-8-6-4-202468
10
Tilt
(m
m/m
)
14001300120011001000
900800700600500400300200100
0
Sub
side
nce
(mm
)
During LW24A
Latest Survey
Predicted Profiles
250
255
260
265
270
275
280
Sur
face
Lev
el A
HD
(m
)
LW 24A
NS
7
HR
F1
HR
F2
HR
F3
HR
F4
HR
F5
HR
F6
HR
F7
HR
F8
HR
F9
HR
F10
HR
F1
1
HR
F12
HR
F13
HR
F14
HR
F1
5
HR
F16
HR
F17
HR
F18
Note: It was predicted that up to 100mm of subsidence may occur in addition to predicted systematic subsidence between LW24A and 200 Panels
I:\Projects\Tahmoor\SurveyData\Inghams\High-Rise Freezer Line (LW24A EOP).grf
Estimated subsidence forPegs HRF6 to HRF17
Upsidence in creekCreek does not extend
to urban area
LW22
LW23A
LW24A
LW24B
Figure 2.2 Observed Subsidence along the High-Rise Freezer Line during Longwall 24A
While subsidence is greater on the tailgate side, tilts and curvatures on the tailgate side are comparatively less than on the maingate side as the shape of the subsidence profile is flatter. For example, maximum tilts on the tailgate side are approximately 8 mm/m, compared to over 10 mm/m on the maingate side along the High-Rise Freezer line.
Mine Subsidence Engineering Consultants 11 Xstrata Coal Tahmoor Colliery Report No. MSEC335 Longwall 24A January 2009 End of Panel Report Subsidence Monitoring Report
The nature and magnitude of the increased subsidence is rare and the cause of the increased subsidence is currently not known. Tahmoor Colliery has commissioned a geotechnical study by Dr Winton Gale of Strata Control Technology to try to identify the cause or causes of the increased subsidence. Results of this study are not yet available as research is continuing. Once it became apparent that increased subsidence had developed, Tahmoor Colliery revised its management plans during extraction of LW24A to manage potential increased impacts to surface infrastructure before the longwall extracted beneath the urban area of Tahmoor.
2.2. Identification of Non-Systematic Subsidence Movements
A plan showing the locations of potential non-systematic movements observed at Tahmoor is shown in Figure 2.3. The locations were selected based on ground monitoring results or observed impacts that appear to have been caused by non-systematic movement. A total of approximately 30 locations (not including valleys) have been identified over the four extracted Longwalls 22 to 24, of which 3 locations are located above Longwall 24A.
Figure 2.3 Map of locations of potential non-systematic movement
Mine Subsidence Engineering Consultants 12 Xstrata Coal Tahmoor Colliery Report No. MSEC335 Longwall 24A January 2009 End of Panel Report Subsidence Monitoring Report
Monitoring lines crossed the locations of non-systematic movement along two monitoring lines. A summary of non-systematic movements at these locations is provided below in Table 2-3.
Table 2-3 Location of New Identified Non-Systematic Movements during Longwall 24A
Monitoring Line or Location
Maximum Upsidence
(mm)
Maximum Strain
(mm/m)
Maximum Tilt(mm/m)
Type Impacts to Surface
Mitchell Close / Lintina Street
(Pegs ML1-LA8)
Not measured as end of
monitoring line -4.8 4.3 Anomaly
Road pavement cracking, adjustment to tension of aerial phone lines
Ralfe Street /Courtland Ave (Pegs RF19-20 and CL1-CL3)
35 (CL1 to CL3)
-3.2 (RF19-20)
5.9 (CL1 to CL3)
Anomaly
5 houses (3xCat 0, 1xCat 1 & 1xCat 4) and compression hump in pavement and kerbs
High-Rise Freezer
(Pegs HRF11-13) 82 -2.5 12.7
Valley upsidence & closure
None (in paddock)
In this table, “upsidence” is defined as the height of the local subsidence bump at the anomaly, as calculated or determined from an otherwise smooth systematic subsidence profile.
The most severe non-systematic movement observed during the mining of Longwall 24A occurred along Lintina Street. The road pavement experienced severe cracking. The movements developed gradually over time and the pavement was repaired on a number of occasions as mining progressed. Photographs of the impacts are shown in Figure 4.1.
Mine Subsidence Engineering Consultants 13 Xstrata Coal Tahmoor Colliery Report No. MSEC335 Longwall 24A January 2009 End of Panel Report Subsidence Monitoring Report
2.3. Bargo River
The location of Longwall 24A relative to the Bargo River is shown in Figure 2.4.
Figure 2.4 Location of Longwall 24A in relation to the Bargo River
race
complete surface flow diversion
throughboulders
boulder
boulders
delaminating rock
race
complete surfaceflow diversion
boulders
flute holes
waterfall
race
boulders
waterfall
boulders
race
waterfall
waterfall
complete surfaceflow diversion flute holes
waterfall
boulder
cracks in cliff
waterfall
crackedtriangularwedge
joint inrockbar
crack inrock
ironprecipitation
and rapidsboulders
race rapids
and rapidsboulders
flute holes
waterfall
joint in rockbar
flute holes
complete surfaceflow diversion
complete surfaceflow diversion
weedscross bed
cross bed
joints
joint
joint
pond
rock shelf
Pencil Falls
rock shelf
rock pond
cliff wall
waterfall
joint in wall
efflorescencewaterfall
iron band
joint
waterfall
crack
rockfall
Walking Trail
GENERAL APPLICATIO
N AREA
RB F
Pool E
Pool F
Pool B
Pool D
RB C
RB E
RB G
Pool H
RB JPool J
Pool L
Pool Q
RB R
Pool N
Pool M
RB M
RB N
RB O
RB P
Pool V
Pool K
Pool O
Pool P
Pool R
Pool SRB S
Pool TRB T
RB U Pool U
RB V
Mermaids
RB K
Pool
RB L
RB Q
Pool W
Water quality sampling (not flow)
Water flow and quality sampling
HCS Bolt
HCS Bolt
HCS Bolt
HCS Bolt
HCS Bolt
HCS Bolt
HCS Bolt
HCS Bolt
HCS Bolt
HCS Bolt
HCS Bolt
HCS Bolt
HCS Bolt
HCS Bolt
HCS Bolt
HCS Logger
HCS Bolt
HCS Logger
HCS Logger
HCS Logger
HCS Logger
Pool A
RB B
RB D
RB H
Pool IRB I
RB APool C
HCS Logger
Water flow and quality sampling
Water flow and quality sampling
Water flow and quality sampling
Water flow and quality sampling
X3L
X2L
X4aL
X4aR
X3R
X1 Line
X6 Li
ne
X6L
X6R
X5c Line
X5b LineX5a Line
X5R
X5L
X4 Line
X4R
X4L
X1R
X1L
X3aR
X3aL
X3a Line
X2 Line
XMP Line
X2R
Dyke
Dyke
LW 25
LW 24A
X3 Line
623 m
Closest distance
of 200 panels to River
Closest distanceof LW24A to River
339 m
Closest distance
of LW25 to R
iver509 m
iron precipitation
iron precipitation
iron precipitation
LW24A Angle of D
raw Line
LW26 A
ngle of Draw
Line
LW25 A
ngle of Draw
Line
iron precipitation
iron precipitation
iron precipitation
Valley Connection Lines
Valley C
onnection Lines
295 m
NOTE:Where possible the valley closure pegs have been linked to the rockbar monitoring lines.Visual inspections fortnightly from Rockbar A to Pool W and Mermaids Pool.
Closure pegs on top of cliffs measured straight across gorge (monthly)
Rockbar monitoring points (end of each longwall)
HCS water level monitoring points (daily)Water flow and quality monitoring (monthly)
LEGEND
X Line
X1L X1R
HCS Logger
HCS water level monitoring points (monthly)HCS Bolt
387 m
Closest distance
to Rockbar I
Closest distance toWaterfall below Pool W
EP14-PEG
X4L-GPS
26-1 NAIL
Gate
ME3-GINSTUMP
ME5-GINSTUMP
25-2 PEG
SITE-GPS-BASE
Angle of Draw Lines
Valley Connection Lines
Mine Subsidence Engineering Consultants 14 Xstrata Coal Tahmoor Colliery Report No. MSEC335 Longwall 24A January 2009 End of Panel Report Subsidence Monitoring Report
A summary of observed subsidence parameters is provided in Table 2-4.
Table 2-4 Summary of Observed Subsidence, Upsidence and Closure along Bargo Gorge Cross Lines
Monitoring Line
Maximum Observed
Subsidence at top of Gorge
(mm)
Maximum Observed
Subsidence at base of Gorge
(mm)
Upsidence (mm)
Closure (mm)
Survey Tolerance ± 5 mm
± 10 mm between top and bottom
of gorge
± 3 mm differential
vertical subsidence
± 3 mm for horizontal distance
across tops of Gorge
Mermaids Pool No pegs Not connected
to datum 0 0
X1 Cross Line Not connected
to datum Not connected
to datum 0 -2 (closure)
X2 Cross Line Not connected
to datum Not connected
to datum 0 -2 (closure)
X3 Cross Line 9 15 0 0
X3a Cross Line 8 11 0 -2 (closure)
X4 Cross Line 8 12 0 -3 (closure)
X4a Cross Line 9 No pegs No pegs -2 (closure)
X5a Cross Line 11 12 0 0
X5b Cross Line 11 12 0 0
X5c Cross Line 11 11 0 0
X6 Cross Line Not connected
to datum Not connected
to datum 0 0
The monitoring results indicate that no measureable upsidence or closure has occurred across any of the monitoring lines across the Bargo Gorge during the mining of Longwall 24A. All differential movements have been very small and close to or within stated survey tolerance.
The observed subsidence is less than 20 mm as predicted. The results indicate that the Gorge may be experiencing a small amount of vertical subsidence of approximately 11 mm or less, based on the more accurate surveys at the tops of the Gorge.
The current observed movements during the mining of Longwall 24A are less than the predicted Longwall 24A maximum incremental upsidence of 20 mm and maximum incremental closure of 50 mm. Given the incised nature of the Gorge and its significant valley height, it was considered possible that actual upsidence and closure movements might exceed predictions but this does not appear to have occurred.
The reason for the lack of valley bulging movement is not known. It is possible that the strata above Longwall 24A had already been stress-relieved by past geological activity. An unusually large amount of vertical subsidence has been observed directly above Longwall 24A. The combination of increased subsidence, tilt and curvature without increased ground strain directly above the goaf suggests that horizontal movements into the goaf have not been substantial, with the predominant direction of ground movement being vertical. The lack of significant differential horizontal movement suggests that mining, therefore, may not have significantly changed the stress environment in the overlying strata in the base of the valley.
Mine Subsidence Engineering Consultants 15 Xstrata Coal Tahmoor Colliery Report No. MSEC335 Longwall 24A January 2009 End of Panel Report Subsidence Monitoring Report
The above comments only represent our considered opinion, which is based on limited facts. Tahmoor Colliery is currently undertaking a geotechnical investigation into the cause of the increased subsidence observed directly above Longwall 24A and the findings of the investigation may shed light on why no measureable upsidence or closure has occurred in the Bargo Gorge.
2.3.1. Angle of Draw Surveys
As shown in Drawing No. MSEC335-01, monitoring lines were installed off the commencing ends of Longwalls 24A, 25 and 26 to measure the extent of vertical subsidence that occurs between the extracted longwalls and the Bargo Gorge. The results of the survey in relation to Longwall 24A are attached to this report.
A summary of observed subsidence parameters along these three monitoring lines is shown in Table 2-5.
Table 2-5 Summary of Observed Subsidence Parameters along Angle of Draw Monitoring Lines
Monitoring Line
Maximum Observed
Subsidence (mm)
Maximum Observed Tilt
(mm/m)
Maximum Observed Tensile
Strain (mm/m)
Maximum Observed
Compressive Strain
(mm/m)
LW 24A Draw Line 1090 10.2 1.3 -0.4
LW 25 Draw Line 12 0.3 0.3 -0.3
LW 26 Draw Line 20 0.4 0.5 -0.5
2.4. Main Southern Railway
The Main Southern Railway was surveyed 17 times on a weekly, twice weekly and thrice weekly basis during the extraction of Longwall 24A. Details of the monitoring undertaken are provided in the monitoring reports prepared by MSEC on behalf of Tahmoor Colliery and these reports have been provided to ARTC throughout the mining period.
The Main Southern Railway experienced a maximum of 40 mm of subsidence during the mining of Longwall 24A. While observed subsidence was greater than predicted (less than 20 mm), the amount of subsidence is very small. Observed maximum incremental tilt was 0.6 mm/m. Observed maximum incremental strain was approximately 0.3 mm/m tensile and 0.5 mm/m compressive (excluding survey marks that have been obviously damaged).
Differential vertical and horizontal movements are relatively small and changes between each survey within survey tolerance. However, elevated ground strain of 0.45 mm/m was measured between 94.600 and 94.620 km. The ground strains represent a closure of 9 mm over a 20 metre bay. Increased ground strain was observed at this site during the mining of Longwall 23A but not during the mining of Longwall 24A. The movements are consistent with valley upsidence and closure movements, as their location coincides with a small watercourse. This watercourse continues beneath the Main Southern Railway through a ballast top bridge culvert at Ch. 94.576 km.
There are a number of locations where irregular subsidence has been observed including 94.260 km, 94.700 km and 95.160 km. These are considered to be due to disturbance of survey marks in the rail corridor in the period between October 2007 and May 2008. All of these bumps have been first observed at the time of first survey since the commencement of Longwall 24A, with nil or minimal change in differential movement for subsequent surveys.
2.4.1. Strain Gauge and Switch Displacement Monitoring
Monitoring in excess of the requirements of the Management Plan for Longwall 24A was conducted as part of the Trial Switch Management Plan. It included continuous rail stress gauge and switch displacement monitoring between 93.900 and 94.400 km.
Small reductions of between 4 and 5 degrees in Stress Free Temperatures (SFT) were observed on the Up and Down Tracks at 94.350 km and 94.400 km from the beginning of May 2008. It is considered that
Mine Subsidence Engineering Consultants 16 Xstrata Coal Tahmoor Colliery Report No. MSEC335 Longwall 24A January 2009 End of Panel Report Subsidence Monitoring Report
these changes are related to mine subsidence. Some dissipation of tensile stress from fixed Continuously Welded Rail (CWR) track into the free rail on the Up Main was observed. Very little change in SFT was observed during the mining of the end of Longwall 24A, which correlates well with measured ground movements.
It is noted that no stress gauges are located near 94.600 km where maximum increases in compressive ground strains have been measured, though it is considered likely that some change in SFT has occurred. This section of track has since been re-stressed.
2.4.2. Thirlmere Way Overbridge
A total of 16 surveys and 38 visual inspections were undertaken of the Thirlmere Way Overbridge on a weekly basis in accordance with the agreed management plans with ARTC and Wollondilly Council.
Measured tilts and strain at the abutments are very small. The results indicate a fall of up to 1.0 mm/m between the bridge abutments from east to west, towards Longwall 24B. Changes in measurements between surveys have been within survey tolerance during the mining of Longwall 24A.
No impacts were observed to the Bridge during the mining of Longwall 24A, as expected following extensive strengthening works undertaken by Tahmoor Colliery prior to commencement of Longwall 24B.
2.4.3. Platform Clearance Surveys
A total of 14 platform clearance surveys were undertaken during the mining of Longwall 24A. All platform clearances are currently greater than minimum design clearances. Measured changes in clearances were within survey tolerance.
2.5. Sewer Infrastructure
One of the key items of infrastructure that had potential to experience impacts as a result of increased subsidence were the self-cleansing sewer pipes within the urban area. Subsidence monitoring was undertaken along the streets and at key sewer pit lids during mining.
Prior to Longwall 24A mining beneath the urban area, the potential changes in sewer grades were re-assessed based on observations along the High-Rise Freezer Line (refer Peg HRF10 in Figure 2.2) for all sewer pipes within the urban area. The reassessment indicated that the grades on the majority of the pipes were expected to remain greater than the minimum grades required for self-cleansing following the mining of Longwall 24A. However, the analysis identified three pipe sections where the projected grades were assessed to be only just greater than the minimum grade required for self-cleansing. The pipes identified were:
SMH30 to SMH31: A 17 metre long section of pipe with a pre-mining grade of 0.79%
SMH31 to SMH32: A 55 metre long section of pipe with a pre-mining grade of 0.71%
SMH25 to SMH26: A 68 metre long section of pipe with a pre-mining grade of 0.98%
A plot of projected changes in grade and projected grades during and after the mining of Longwall 24A is provided in Figure 2.5. The projected changes in grade are primarily based on observed monitoring results along the High-Rise Freezer Line. The projected values were compared with observations based on subsidence measured at nearby survey marks, which are also shown in Figure 2.5.
Relative height differences between the sewer pit lids for four identified pipe sections were measured three times a week in accordance with an agreed management plan with Sydney Water. A total of 29 surveys were conducted along the above pipe sections during the mining of Longwall 24A. A plot of observed height differences and changes in grade is provided in Figure 2.6. The results are compared with projected sewer grades, which were based on observations along the High-Rise Freezer line.
It can be seen from Figure 2.6 that changes in sewer grade have occurred and the changes in grade appear to be less than the grades that have been projected to develop based on observed monitoring results along the High-Rise Freezer Line.
Mine Subsidence Engineering Consultants 17 Xstrata Coal Tahmoor Colliery Report No. MSEC335 Longwall 24A January 2009 End of Panel Report Subsidence Monitoring Report
It can be seen that the pipes between SMH30 and SMH31, and SMH31 to SMH32 had initially reduced as the longwall passed directly beneath it, but the grade has gradually improved as the longwall progressed away from the pipe. The pipe section is located near the centre of the longwall and is oriented almost parallel to the longitudinal direction of the longwall. The observed grades were expected as the pipe section was largely influenced by travelling tilts as the subsidence wave approached and passed the pipes. All grades remained positive and self-cleansing.
Figure 2.5 Projected & Observed Subsidence Profiles along selected Sewer Line during LW 24A
0 50 100 150 200 250 300 350 400 450 500 550 600 650Distance along Sewer Line from Survey Mark R23 (m)
-0.20.00.20.40.60.81.01.21.41.61.82.0
Gra
de (
%)
LW 24A
Initial Grade
-8
-6
-4
-2
0
2
4
6
8
10
Cha
nge
in G
rade
(m
m/m
)(P
ositi
ve =
incr
ease
in fa
ll)
120011001000
900800700600500400300200100
0
Sub
side
nce
(mm
) Projected Subsidenceusing HRF surveysup to 7 May 2008
(distances are lengthof LW 24A)
Proj @ 991m
Proj @ 950m
Proj @ 900m
Proj @ 850m
Proj @ 800m
Proj @ 750m
Proj @ 700m
Observed during LW24A
Latest Observedat 990.6m
REM
EMBR
ANC
E D
VE
LW N
o.24A
250
255
260
265
270
275
280
285
290
Sur
face
Lev
el A
HD
(m
)
LW 24A
R23 M
L6
ML5
ML4
ML3
ML2
ML1
LA8
LA7
LA6
LA5
LA4
LA3
RF
19
RF
20
RF
21
RF
22
RF
23
RF
24
RF
25
RF
26
RF
27
RF
28
RF
29
RF
30
1.38% 0.98% 1.20%1.64% 0.71% 0.79% 0.89%
0.96%SMH 26 SMH 25
SMH 32SMH 31
SMH 30 SMH 29SMH 28
I:\Projects\Tahmoor\SurveyData\Sewer Mains\Sewer Line Predicted.grf
Mine Subsidence Engineering Consultants 18 Xstrata Coal Tahmoor Colliery Report No. MSEC335 Longwall 24A January 2009 End of Panel Report Subsidence Monitoring Report
Figure 2.6 Projected and Observed Changes in Grade between selected Sewer Pits
-300 -200 -100 0 100 200 300 400Distance between Longwall Face and Mid-Point between Sewer Pits (positive value when LW past Mid-pt) (m)
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
1.8
Pip
e G
rad
ebe
twee
n S
ewer
Pits
(%
)
Average Grade for SewerPipe between Sewer Pits(includes pre-mining gradeand estimated change ingrade due to subsidenceat time of initial survey)
SMH29 to SMH30
Proj 29 to 30
SMH30 to SMH31
Proj 30 to 31
SMH31 to SMH32
Proj 31 to 32
SMH25 to SMH26
Proj 25 to 26
-300 -200 -100 0 100 200 300 400Distance between Longwall Face and Mid-Point between Sewer Pits (positive value when LW past Mid-pt) (m)
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
He
ight
Diff
ere
nce
bet
wee
n S
ewer
Pits
(m
)
Measured Height Differencebetween Sewer Pits(raw survey data only)
SMH29 to SMH30
SMH30 to SMH31
SMH31 to SMH32
SMH26 to SMH25
-300 -200 -100 0 100 200 300 400Distance between Longwall Face and Survey Mark (positive value when LW past mark) (m)
900
800
700
600
500
400
300
200
100
0
Sub
side
nce
(mm
)
Subsidence at Survey Peg(including estimate of
subsidence prior to initial survey of each peg)
RF19
RF22
LA3
ML3
ML6
LW No.24A
RE
ME
MB
RA
NC
E D
VE
SMH26
SMH25
SMH32 SMH
30
SMH29
SMH31
ML6 LA3
ML3
RF19 RF22
0 50 100 150 200 250 300 350 400 450 500 550 600 650Distance along Sewer Line from Survey Mark R23 (m)
250
255
260
265
270
275
280
285
290S
urfa
ce L
evel
AH
D (
m)
LW 24A
R2
3 ML
6
ML
5
ML
4
ML
3
ML
2
ML
1
LA8
LA7
LA6
LA5
LA4
LA3
RF
19
RF
20
RF
21
RF
22
RF
23
RF
24
RF
25
RF
26
RF
27
RF
28
RF
29
RF
30
1.38% 0.98% 1.20%1.64% 0.71% 0.79% 0.89%
0.96%SMH 26 SMH 25
SMH 32SMH 31
SMH 30 SMH 29SMH 28
I:\Projects\Tahmoor\SurveyData\Sewer Mains\Key Sewer Grades LW24A.grf
SURVEY DATE: 28 JULY 08 Length of LW: 991.6 m - Complete
Mine Subsidence Engineering Consultants 19 Xstrata Coal Tahmoor Colliery Report No. MSEC335 Longwall 24A January 2009 End of Panel Report Subsidence Monitoring Report
2.6. Power Pole Surveys
A total of 21 surveys of selected power poles were conducted in accordance with the agreed management plan with Integral Energy. No impacts were observed to any power pole during the mining of Longwall 24A as expected.
Of the poles that were surveyed, maximum subsidence of 489 mm was observed at Pole 240 on Lintina Street. A maximum horizontal movement of 109 mm was measured at the top of the same pole.
2.7. Tahmoor Town Centre
A total of 3 detailed surveys of the Tahmoor Town Centre and basement carpark were undertaken in accordance with the conditions of SMP Approval by the Department of Primary Industries. Maximum observed subsidence was 41 mm at the south-east corner of the complex.
2.8. Inghams
2.8.1. Ground and Building Monitoring Results
Ground and building surveys have been conducted in accordance with the Management Plan. The locations of monitoring lines relative to Longwall 24A and the Inghams infrastructure are shown in Drawing No. MSEC341-01 and a summary of maximum observed subsidence parameters for each monitoring line is provided in Table 2-6.
Table 2-6 Summary of Maximum Observed Subsidence Parameters
Monitoring Line
Maximum Observed
Subsidence (mm)
Maximum Observed
Tilt (mm/m)
Maximum Observed
Tensile Strain
(mm/m)
Maximum Observed
Compressive Strain
(mm/m)
Dam Line 762 4.7 0.5 -0.3
East-West Line 602 6.4 1.0 -0.2
North-South Line 174 0.5 0.1 -0.2
High-Rise Freezer Line
11692 12.7 1.03 -2.53
Plant Perimeter Line
1181 Please refer Table 2-7 for differential vertical and horizontal
movements.
Pipe Support Line 1081 Please refer Table 2-7 for differential vertical and horizontal
movements.
1 Observed subsidence along the Plant Perimeter Line and Pipe Support Line are less than other monitoring lines because they were installed just after the commencement of Longwall 24A. Based on surveys from the survey origin, it is estimated that 5 mm of subsidence occurred prior to the installation of these monitoring lines and it is recommended that this amount be added to the monitoring results. Pipe Support Marks 16 to 23 were installed as part of the Stage 2 Management Plan. Approximately 23 mm of subsidence had been measured near these pegs at this time. 2 High-Rise Freezer line was extended from HRF5 to HRF18 while Longwall 24A had stopped at 389 metres of extraction.
2.8.2. Ammonia Pipes
The Management Plan includes planned procedures that are triggered from results of monitoring in relation to ammonia pipes. The triggers for the blue trigger level are:
Ground survey: Differential vertical or horizontal movement of 10 mm between adjacent survey marks on the Plant Perimeter and Pipe Support Monitoring Lines
Displacement transducers: 10 mm movement since re-commencement of Longwall 24A
Mine Subsidence Engineering Consultants 20 Xstrata Coal Tahmoor Colliery Report No. MSEC335 Longwall 24A January 2009 End of Panel Report Subsidence Monitoring Report
Pipe Stress Transducers: 82.8 MPa for low temp pipes and 112.5 MPa for high temp pipes
Ground survey
A summary of maximum observed differential vertical and horizontal movements along these monitoring lines are shown in Table 2-7.
Table 2-7 Summary of Maximum Observed Differential Movements along Plant Perimeter and Pipe Support Monitoring Lines
Monitoring Line
Maximum Observed
Subsidence (mm)
Maximum Observed
Differential Vertical
Movement (mm)
Maximum Observed
Differential Horizontal Movement
(mm)
Is BLUE trigger exceeded?
Plant Perimeter Line 1241 -10.7 to +9.4 -3.0 to +3.0 YES
Pipe Support Line 1131 -5.2 to +2.9 -1.0 to +6.0 NO 1 Please refer Note 1 for Table 2-6.
Differential vertical movements exceeded the blue trigger between survey marks Plant 11 and Plant 12, which are located on the southern side of the Carton Tunnel. The pegs are spaced approximately 21 metres apart and the corresponding ground tilt is therefore 0.5 mm/m. The measured differential horizontal movements were within survey tolerance.
Displacement transducers
The measured displacements for Sensors 2 and 3 exceeded the BLUE trigger on a number of occasions. However, the sensors were later found to be faulty. It is considered that the actual displacements did not exceed the trigger levels.
2.8.3. Pipe Stress Transducers (PSTs)
While some pipe stress transducers showed slight changes in stress, the majority of stress gauges did not reach the trigger level, except for intermittent spikes that were considered to be due to either electrical interference or influence of compressor operation. Only one gauge was observed to experience an increase in pipe stress. The pipe supports were adjusted during mining and the stresses were subsequently reduced.
2.8.4. Discussion
The subsidence associated with the Inghams Plant occurred in accordance with predictions. Increased subsidence above predictions obtained by the Incremental Profile Model was observed at the Plant during the mining of Longwall24A. However, this was predicted as the Plant was located above mostly solid, unmined coal reserves that lay between a previously mined area (200 Panels) and the currently mined Longwall 24A. Observations of increased subsidence had been experienced in similar previous mining situations and these are believed to be due to a regional relaxation of the insitu stresses in the overlying strata.
As discussed in the Management Plan, it was expected that this increased subsidence would be accompanied by low tilts and strains, and this was observed during the mining of Longwall 24A. It can be seen from the monitoring results that observed tilts and strains similar to or less than survey tolerance in the vicinity of the Inghams Plant and along nearby monitoring lines (North-South, High-Rise Freezer). A total variation of approximately 38 mm of subsidence was observed among all survey pegs along the Plant Perimeter and Pipe Support Monitoring Lines.
While subsidence developed as expected at the Plant, increased subsidence was observed at the dams. This was not predicted.
Mine Subsidence Engineering Consultants 21 Xstrata Coal Tahmoor Colliery Report No. MSEC335 Longwall 24A January 2009 End of Panel Report Subsidence Monitoring Report
CHAPTER 3. SUMMARY OF SURVEYS AND INSPECTIONS
Many surveys and inspections were required to be conducted to meet the requirements of the Surface, Safety and Serviceability Management Plan. Due to the complexities involved, surveys and inspections were managed using a computer database on a weekly basis. A register was also kept, detailing when each survey and inspection had been completed. A timeline showing when each type of survey and inspection was conducted is shown in Fig. 3.1 and Fig. 3.2.
Fig. 3.1 Timeline and Surveys and Inspections during Longwall 24A (Part 1 of 2)
I:\Projects\Tahmoor\MSEC335 - Monitoring LW24A\LW24A - End of Panel Report\Survey and Inspection Timelines LW24A.grf
Nov-07 Dec-07 Jan-08 Feb-08 Mar-08 Apr-08 May-08 Jun-08 Jul-08 Aug-08 Sep-08
Nov-07 Dec-07 Jan-08 Feb-08 Mar-08 Apr-08 May-08 Jun-08 Jul-08 Aug-08 Sep-08
LW 24A
LW 24A
Thirlmere Way Overbridge Visual Inspections
Thirlmere Way Overbridge Surveys
Subsidence reports for Railway
Reports for Monitoring Results
Groundwater Water Quality Sampling - Lab
Groundwater Water Quality Sampling - Field
Groundwater Water Levels
Redbank Ck Water Quality Sampling - Lab
Redbank Ck Water Quality Sampling - Field
Redbank Ck Data Logger Downloads
Myrtle Ck Water Quality Sampling - Lab
Myrtle Ck Water Quality Sampling - Field
Myrtle Ck Data Logger Downloads
Bargo River Rockbar Monitoring Surveys
Bargo River Valley Closure Surveys
Bargo River Angle of Draw Surveys
Bargo River Visual Monitoring
Bargo River Water Quality Sampling
Bargo River Water Level Surveys
Bargo River Data Logger Downloads
Bargo River Flow Gauging
Tanya Pl
Remembrance Dve
Ralfe St
Progress St
Pandora Pl
Mitchell Cl
Lintina St
Larkin St
Emmett St
Courtland Ave
Bradbury St
Castlereagh St
Chapman St
Thirlmere Way
Main Southern Railway Corridor
Natural Features
Ground Monitoring Surveys
Main Southern Railway
Mine Subsidence Engineering Consultants 22 Xstrata Coal Tahmoor Colliery Report No. MSEC335 Longwall 24A January 2009 End of Panel Report Subsidence Monitoring Report
Fig. 3.2 Timeline and Surveys and Inspections during Longwall 24A (Part 2 of 2)
I:\Projects\Tahmoor\MSEC335 - Monitoring LW24A\LW24A - End of Panel Report\Survey and Inspection Timelines LW24A - 2.grf
Nov-07 Dec-07 Jan-08 Feb-08 Mar-08 Apr-08 May-08 Jun-08 Jul-08 Aug-08 Sep-08
Nov-07 Dec-07 Jan-08 Feb-08 Mar-08 Apr-08 May-08 Jun-08 Jul-08 Aug-08 Sep-08
LW 24A
LW 24A
Visual Inspections
Building Surveys
Telstra Visual Inspections
Power Pole Surveys
Choke Report
Sewer Main Surveys
Dams
Pools and pool gates
Houses
Public Amenities / Commercial District
Dam Line
East-West Line
North-South Line
HIgh-Rise Freezer Line
Plant Line
Pipe Support Line
Weighbridge
BC Line
Visual Inspections
Wall & Column Tilt Surveys
Building Interface Surveys
Remembrance Drive Bridge Survey
Tahmoor Town Centre
Sydney Water - Sewer
Structure Inspections
Integral Energy - Electrical
Telstra - Telecommunications
Inghams
Agility - Gas
Mine Subsidence Engineering Consultants 23 Xstrata Coal Tahmoor Colliery Report No. MSEC335 Longwall 24A January 2009 End of Panel Report Subsidence Monitoring Report
A count of surveys and inspections is provided in Table 3-1.
Table 3-1 Number of Surveys and Inspections conducted during Longwall 24A
Inspection / Survey Responsibility Number of Inspections / Surveys
Ground Monitoring Surveys
Main Southern Railway Corridor Meadows Consulting 17
Bradbury Street Lean & Hayward 1
BC Line Lean & Hayward 12
Castlereagh Street Lean & Hayward 1
Chapman Street Lean & Hayward 1
Courtland Avenue Lean & Hayward 11
Emmett Street Lean & Hayward 9
Larkin Street Lean & Hayward 9
Lintina Street Lean & Hayward 11
LW24A Draw Line Lean & Hayward 7
LW25 Draw Line Lean & Hayward 7
LW26 Draw Line Lean & Hayward 7
Mitchell Close Lean & Hayward 9
Pandora Place Lean & Hayward 9
Progress Street Lean & Hayward 8
Ralfe Street Lean & Hayward 14
Remembrance Drive Lean & Hayward 20
Remembrance Drive Shopfronts Lean & Hayward 1
Tanya Place Lean & Hayward 10
Thirlmere Way Lean & Hayward 12
Sub-Total 176
Natural Features
Bargo River flow gauging HCS 8
Bargo River data logger downloads HCS 8
Bargo River water level surveys HCS 9
Bargo River water quality sampling - field & lab
Geoterra 6
Bargo River visual inspections Tahmoor Colliery, Geoterra, HCS 32
Bargo River Angle of Draw Surveys Lean & Hayward 7
Bargo River Valley Closure Surveys Lean & Hayward 7
Bargo River Rockbar Monitoring Surveys
Lean & Hayward 4
Myrtle Creek - Download Level Data Loggers (bi-monthly)
Geoterra 3
Myrtle Creek - Water Quality Geoterra 3
Mine Subsidence Engineering Consultants 24 Xstrata Coal Tahmoor Colliery Report No. MSEC335 Longwall 24A January 2009 End of Panel Report Subsidence Monitoring Report
Inspection / Survey Responsibility Number of Inspections / Surveys
sampling - Field (bi-monthly)
Myrtle Creek - Water Quality Sampling - Lab (quarterly)
Geoterra 3
Redbank Creek - Download Level Data Loggers (bi-monthly)
Geoterra 3
Redbank Creek - Water Quality sampling - Field (bi-monthly)
Geoterra 3
Redbank Creek - Water Quality Sampling - Lab (quarterly)
Geoterra 3
Groundwater - Water levels in piezometers (bi-monthly)
Geoterra 3
Groundwater - Water Quality sampling - Field (bi-monthly)
Geoterra 3
Groundwater - Water Quality Sampling - Lab (quarterly)
Geoterra 3
Sub-Total 109
Main Southern Railway (note Corridor survey above)
Reports for continuous discrete rail stress transducers monitoring results
Pidgeon Civil Engineering 13
Subsidence monitoring reports MSEC 6
Tahmoor Station Platform Clearance Surveys
Meadows Consulting 14
Thirlmere Way Overbridge surveys Meadows Consulting 16
Thirlmere Way Overbridge visual inspections
Sunrise 38
Sydney Water - Sewer
Sewer Main Surveys Lean & Hayward 28
Integral Energy - Electrical
Power Pole surveys Lean & Hayward 21
Telstra - Telecommunications
Visual inspections Lutibo (Colin Dove) 13
Tahmoor Town Centre
Building surveys Lean & Hayward 3
Structure Inspections
Public amenities / commercial district
Sunrise 3630
Houses, Units and Aged Care Villages
Sunrise 196
Pools and pool gates Sunrise 13
Dams Geoterra 18
Sub-Total 3856
Mine Subsidence Engineering Consultants 25 Xstrata Coal Tahmoor Colliery Report No. MSEC335 Longwall 24A January 2009 End of Panel Report Subsidence Monitoring Report
Inspection / Survey Responsibility Number of Inspections / Surveys
Inghams
Dam Line Lean & Hayward 30
East-West Line Lean & Hayward 30
North-South Line Lean & Hayward 30
High-Rise Freezer Line Lean & Hayward 30
Plant Line Lean & Hayward 29
Pipe Support Line Lean & Hayward 28
Weighbridge Lean & Hayward 18
Wall & Column Tilt Surveys Sunrise 58
Building Interface Surveys Sunrise 105
Visual Inspections Sunrise 145
Sub-Total 503
Mine Subsidence Engineering Consultants 26 Xstrata Coal Tahmoor Colliery Report No. MSEC335 Longwall 24A January 2009 End of Panel Report Subsidence Monitoring Report
CHAPTER 4. IMPACTS TO SURFACE FEATURES
4.1. Summary of Impacts to Surface Features
A comparison between predicted and observed impacts to surface features is summarised in Table 4-1 below. The predicted and observed impacts to surface features compare reasonably well, with the exception of locations where non-systematic movements have occurred.
Table 4-1 Summary of Predicted and Observed Impacts during Longwall 24A
SURFACE FEATURE PREDICTED IMPACTS OBSERVED IMPACTS
NATURAL FEATURES
Bargo River Potential cracking and uplift of river bed. Potential for observable loss of flow and pool level reduction Potential reduction in water quality Potential for transfer of water to shallow groundwater system Please refer report by Geoterra.
No cracks or uplift observed. No loss of stream flow or pool level reductions observed No observable reduction in quality No transfer of water to shallow groundwater observed Please refer report by Geoterra.
Aquifers or Known Groundwater Resources
Potential for enhanced groundwater seepage from the cliffs Temporary lowering of piezometric surface by up to 10m which may stay at that level until maximum subsidence develops Groundwater levels should recover with no permanent post mining reduction in water levels in bores on the plateau unless a new outflow path develops No permanent reduction in groundwater levels under the Bargo River Please refer report by Geoterra.
No change in cliff seepage flow or water quality observed Lowering of piezometric surface by up to 8.9m in piezometer P2 has been observed Groundwater levels in P2 have recovered by approximately 8.6m from their lowest point over approximately the last 12 months No reduction in groundwater levels under the Bargo River have been observed Please refer report by Geoterra.
Steep slopes and cliffs Potential soil slippage and cracking to slopes. Large-scale slope failures or cliff instabilities unlikely.
No impacts observed during Longwall 24A though 4 small natural rock falls occurred.
Natural Vegetation No impacts anticipated. No impacts observed during Longwall 24A.
PUBLIC UTILITIES
Railways No impact to track geometry likely if systematic movements occur.
Observed loss of rail stress free temperature of 4 to 5oC. Rail restressed. No impact to track geometry.
Roads (All Types) Minor cracking and buckling may occur in isolated locations.
Cracks and buckling in pavements on Lintina Street and Courtland Avenue. Cracks and buckling in kerbs and gutters along Remembrance Drive.
Water Pipelines Minor impacts possible to pipelines, particularly older cast iron pipes with lead joints.
No impacts observed during Longwall 24A.
Gas Pipelines Ground movements unlikely to adversely impact pipelines if
No impacts observed during Longwall 24A.
Mine Subsidence Engineering Consultants 27 Xstrata Coal Tahmoor Colliery Report No. MSEC335 Longwall 24A January 2009 End of Panel Report Subsidence Monitoring Report
Table 4-1 Summary of Predicted and Observed Impacts during Longwall 24A
SURFACE FEATURE PREDICTED IMPACTS OBSERVED IMPACTS
systematic movement occurs.
Sewerage Pipelines Mining induced tilt may reduce gradient of some pipes to less than that required for self-cleansing. Cracking to pipes and joints are unlikely if systematic movement occurs. Potential impacts at creek crossings where non-systematic movement is expected.
No impacts observed during Longwall 24A.
While grades for some pipes were reduced, none experienced a reversal of grade. Sydney Water advises that no pipes require re-levelling.
Electricity Transmission Lines or Associated Plants
Ground movements unlikely to adversely impact electrical infrastructure if systematic movement occurs.
No impacts observed during Longwall 24A.
Telecommunication Lines or Associated Plants
Ground movements unlikely to adversely impact telecommunications infrastructure if systematic movement occurs. Most vulnerable cables are older cables such as air pressurised lead sheathed cables. Strains may be higher where they connect to support structures or where affected by tree roots.
Retensioned consumer lines on Huen Pl, Pimelia St, Winpara Cl and Leiha Pl as precautionary measure.
PUBLIC AMENITIES Potential impacts to public amenities, particularly shops along Remembrance Drive. All public amenities expected to remain safe and serviceable due to the mining of Longwall 24A.
Separation of construction joint in one shop on Remembrance Drive. All structures remained safe and serviceable during mining.
FARMLAND AND FACILITIES
Farm Buildings or Sheds Negligible to slight impacts predicted for all farm buildings and sheds if systematic movement occurs.
No impacts observed during Longwall 24A.
Fences Potential for impacts to fences and gates. Gates are most vulnerable.
No impact on fences on farmland.
Farm Dams Potential adverse effects on dam walls and storage capacity. Please refer report by Geoterra.
No impacts observed to farm dams during Longwall 24A. Please refer report by Geoterra.
Wells or Bores No registered usage within SMP Area. Please refer report by Geoterra.
Water depressurisation observed in water bores. Please refer report by Geoterra.
INDUSTRIAL, COMMERCIAL & BUSINESS ESTABLISHMENTS
Negligible to slight impacts predicted for all business and commercial establishments.
Separation of construction joint in one shop on Remembrance Drive. Separation of floor slab joint and reversal of grade to connecting pipe between dams at Inghams Plant.
AREAS OF ARCHAEOLOGICAL OR HERITAGE SIGNIFICANCE
Negligible to very impacts predicted for items of heritage significance.
No impacts observed during Longwall 24A.
PERMANENT SURVEY Ground movement predicted at Ground movement occurred.
Mine Subsidence Engineering Consultants 28 Xstrata Coal Tahmoor Colliery Report No. MSEC335 Longwall 24A January 2009 End of Panel Report Subsidence Monitoring Report
Table 4-1 Summary of Predicted and Observed Impacts during Longwall 24A
SURFACE FEATURE PREDICTED IMPACTS OBSERVED IMPACTS
CONTROL MARKS identified survey marks.
RESIDENTIAL ESTABLISHMENTS
Houses, flats or units Status as at 24 August 2008 (two days after the start of Longwall 25).
Predictions and impact assessments provided for individual structures based on systematic subsidence movements. Of the 1,016 houses and public amenities within zone of influence of LWs 22 to 24A, 492 structures assessed to have Strain Category 1 or 2. Potential for impacts to occur as a result of non-systematic movement. Potential for some structures to experience minor impacts that may only be classified as Tilt Category A or Strain Category 1. All houses expected to remain safe, serviceable and repairable provided that they are in sound condition prior to mining.
No. of properties that have reported impacts after LW 24A = 160 (32 claims during LW 24A). No. of properties with impacts that relate to a residential structure = 147 (31 claims during LW 24A). No. of properties with impacts that only relate to associated structures = 13 (1 claim during LW 24A). Some structures are considered to have experienced impacts due to non-systematic movements. No structures have been identified as being either unsafe or unserviceable at this time. However, MSB have decided that cost of repair is greater than cost of replacement for four houses, one of which is located above LW 24A. Please refer details in this report.
Retirement or Aged Care Villages Longwall 24A will not Macquarie Grove Retirement Village
No impacts during mining of Longwall 24A.
Swimming Pools While predicted tilts are not expected to cause a loss in capacity, tilts are more readily noticeable in pools as the height of the freeboard will vary along the length of the pool. While predicted strains impacts are low, many of the pools are in-ground, which are more susceptible.
Impacts to 12 swimming pools during mining of LWs 22 to 24A. No impacts to pools due to mining of LW 24 A.
Associated Structures such as Workshops, Garages, On-Site Waste Water Systems, Water or Gas Tanks or Tennis Courts
Potential impact to pipes connected to in-ground septic tanks.
Negligible impacts predicted for non-residential domestic structures, including sheds and tanks.
Minor impacts to 23 structures during mining of LWs 22 to 24A. Impacts to 3 structures above Longwall 24A.
External Residential Pavements Cracking and buckling likely to occur, though majority minor.
Impacts to pavements observed on 61 properties during mining of Longwalls 22 to 24A. Impacts to 3 pavements above Longwall 24A.
Fences in Urban Area Some fences and gates could be slightly damaged. Most vulnerable are colorbond fences.
Impacts to gates and fences observed on 44 properties during mining of Longwalls 22 to 24A. Impacts to 3 properties above Longwall 24A.
Mine Subsidence Engineering Consultants 29 Xstrata Coal Tahmoor Colliery Report No. MSEC335 Longwall 24A January 2009 End of Panel Report Subsidence Monitoring Report
4.2. Bargo River Gorge
4.2.1. Water Quality and Flow Impacts
Geoterra undertook an investigation into the effects of Longwall 24A on surface and ground waters in the area (Geoterra, 2008). Geoterra reported no cracks or riverbed uplift observed during mining and no observed impacts to pool levels, water flow or quality.
No adverse effect on stream water quality due to subsidence effects following extraction of Longwall 24A have been observed in the Bargo River for the monitored salinity, metals and nutrients. This is supported by the observation that the sulfate, as well as lithium, barium and strontium concentrations within the SMP Area also do not show any increase or decrease from changes in groundwater flow into or out of the river following extraction of Longwall 24A.
Field inspections, monitoring and laboratory analyses conducted to date have shown no increase the seepage volume, iron hydroxide precipitation or changes in other monitored water quality parameters within any pool containing a ferruginous groundwater seep within or outside the SMP area, either before or since Longwall 24A was extracted.
4.2.2. Rockfalls
Four very minor rockfalls have been observed during mining, though each of these has been observed following significant rainfall or wind events. The rock falls are referred to as RF-1, RF-A, B and C. Similar minor rockfalls were observed prior to mining.
A geotechnical inspection of the rockfalls was completed by Pells Sullivan Meynink (May 2008) and information below has been drawn from this report. No single factor can be identified as the cause of all the rock falls.
RF-1 lies below a relatively unstable portion of gorge wall and the morphology and condition of debris in the fall zone indicate that this has been and will continue to be an area of high rock fall potential. There is a strong correlation between rainfall intensity and RF-1.
RF-A, B and C represent single events that occurred in relatively stable regions of the gorge (plateau with thick vegetation). The presence of a water flow path down the cliff line in the location of RF-A suggests that a small rainfall event may have contributed to this rock fall.
The triggers of the four rock falls were assessed by PSM to be:
Increased rainfall and wind; and/or
Rapid changes in temperature and humidity.
There is no evidence to show that mining activity is directly responsible for any of the four rock falls and hence a mining associated trigger is considered unlikely. Given the unstable nature of cliffs, it is very difficult to know whether mine subsidence has contributed to these very minor rockfalls. However, given that no upsidence or closure is apparent across any of the monitoring lines, it is considered that any contribution from mining would be very small.
4.2.3. Exceedence of Defined Triggers
During the mining of Longwall 24A no triggers associated with the Tahmoor Colliery Longwall 24 to 26, Natural Features, Surface Safety Serviceability and Management Plan (Rev G, November 2007) have been reached or exceeded.
No remediation works have been required.
4.3. Main Southern Railway
No impacts were observed during the daily visual inspections.
As discussed in Section 2.34, small reductions in SFT between 4 and 5 degrees were observed during the mining of Longwall 24A. In accordance with the agreed management plan with ARTC, the rail was re-stressed and restored to pre-mining condition following cessation of subsidence from Longwall 24A.
Mine Subsidence Engineering Consultants 30 Xstrata Coal Tahmoor Colliery Report No. MSEC335 Longwall 24A January 2009 End of Panel Report Subsidence Monitoring Report
4.3.1. Thirlmere Way Overbridge
No impacts were observed to the Bridge, as expected following extensive strengthening works undertaken by Tahmoor Colliery prior to commencement of Longwall 24B.
4.3.2. Exceedence of Defined Triggers
During the mining of Longwall 24A one of the triggers associated with the Tahmoor Colliery Longwall 24 to 26, Main Southern Railway Surface Safety Serviceability and Management Plan (Rev D, September 2006) was exceeded. The trigger was an observed incremental subsidence exceeding 10 mm, which is above predictions of systematic movement.
No remediation action was required in relation to this trigger exceedence. The extent of monitoring along the rail corridor was increased, in accordance with the Management Plan.
4.4. Roads
Approximately 10.3 kilometres of asphaltic pavement lie directly above the extracted longwalls and a total of 12 impacts have been observed. The observed rate of impact equates to an average of one impact for every 860 metres of pavement. The impacts were minor and did not present a public safety risk.
One of these impact sites, located on Lintina Street above Longwall 24A, was substantially greater than the other 11 impact sites. A selection of photographs is provided in Figure 4.1. The impacts on Lintina Street were repaired twice as the longwall progressed.
Cracks to kerbs and gutters were also observed in isolated locations on Courtland Avenue and Remembrance Drive.
4.4.1. Exceedence of Defined Triggers
During the mining of Longwall 24A one of the triggers associated with the Tahmoor Colliery Longwalls 24 to 26, Wollondilly Shire Council Roads, Bridges and Culverts, Surface Safety Serviceability and Management Plan (Rev B) was exceeded. The trigger exceeded was impacts to road pavements. The impacts have been recorded by the MSB and will be repaired. Temporary repairs have been conducted along Lintina Street.
Mine Subsidence Engineering Consultants 31 Xstrata Coal Tahmoor Colliery Report No. MSEC335 Longwall 24A January 2009 End of Panel Report Subsidence Monitoring Report
Photographs courtesy of Tahmoor Colliery and Colin Dove
Figure 4.1 Photographs of impacts to road pavements and kerbs during Longwall 24A
Lintina Street Lintina Street
Remembrance Drive
Mine Subsidence Engineering Consultants 32 Xstrata Coal Tahmoor Colliery Report No. MSEC335 Longwall 24A January 2009 End of Panel Report Subsidence Monitoring Report
4.5. Potable Water Infrastructure
Longwalls 22 to 24A have directly mined beneath approximately 960 metres of DICL pipe and 2.7 kilometres of CICL pipe, with only one noticeable impact recorded. This was a leak in a cast iron water main on Glenanne Place in June 2007. A very small number of minor leaks have been observed to consumer connection pipes on private properties
During the mining of Longwall 24A no impacts were observed to water mains above the longwall. No remediation was required.
4.5.1. Exceedence of Defined Triggers
During the mining of Longwall 24A no triggers associated with the Sydney Water Potable Water Infrastructure Surface Safety Serviceability and Management Plan (Rev E) were exceeded and no remediation was required.
4.6. Gas Infrastructure
It is noted that Longwalls 22 to 24A have directly mined beneath approximately 6.0 kilometres of gas pipes and no impacts have been recorded so far.
Subsidence monitoring and enhanced gas patrols were undertaken along the streets during mining. Increased subsidence has been observed above Longwall 24A with no impacts to gas infrastructure.
4.6.1. Exceedence of Defined Triggers
During the mining of Longwall 24A no triggers associated with the Tahmoor Colliery Longwalls 24 to 26 Alinta (now Jemena) Asset Management Surface Safety Serviceability and Management Plan (Rev E) were exceeded and no remediation was required.
4.7. Sewer Infrastructure
Longwalls 22 to 24A have directly mined beneath approximately 8.1 kilometres of sewer pipes. While changes in sewer grade have occurred as a result of mine subsidence, no noticeable impacts have been recorded so far. The observed frequency of incidences is similar to those in areas not affected by subsidence.
Subsidence monitoring was undertaken along the streets and at key sewer pit lids during mining as outlined in Section 2.5. Increased subsidence has been observed above Longwall 24A with no reported leakage, blockage or reversal of grade of the sewers.
4.7.1. Exceedence of Defined Triggers
During the mining of Longwall 24A one of the triggers associated with the Tahmoor Colliery Longwall 24 to 26, Sydney Water Sewer Infrastructure, Surface Safety Serviceability and Management Plan (Rev E, August 2008) was exceeded. The trigger exceeded was the minimum grade required for self cleansing of the sewer (i.e. less than 4 mm/m or 0.4%), and this occurred at SMH31-32.
On 23 May, the grade for SMH31 to SMH32 was measured to be 0.39%, which was less than the first trigger level of 0.4 % in the agreed management plan with Sydney Water. This trigger level was set as an early warning of potential impacts, where consideration would be given to tanker flush the affected sewer pipes. A teleconference was convened on 23 May, where Sydney Water recommended that tanker flushing not commence and to continue monitoring. It was agreed to re-set the trigger level to 0.3 % based on the observed gradual change in grade. On 27 May, it was apparent from the monitoring results that the grade would soon reduce below 0.3 % and it was agreed at a scheduled teleconference to re-set the trigger level to 0.2 % based on the observed gradual change in grade. The minimum grade at the end of Longwall 24A was 0.28 %.
Mine Subsidence Engineering Consultants 33 Xstrata Coal Tahmoor Colliery Report No. MSEC335 Longwall 24A January 2009 End of Panel Report Subsidence Monitoring Report
4.8. Electrical Infrastructure
Longwalls 22 to 24A have directly mined beneath approximately 16.7 kilometres of electrical cables and 380 power poles and no noticeable impacts have been recorded so far.
Subsidence monitoring and daily visual inspections were undertaken along the streets during mining of Longwall 24A. While increased subsidence has been observed above Longwall 24A there were no reported impacts to electrical infrastructure.
4.8.1. Exceedence of Defined Triggers
During the mining of Longwall 24A no triggers associated with the Tahmoor Colliery Longwall 24 to 26, Integral Energy Surface Safety Serviceability and Management Plan (Rev C, August 2006) were exceeded and no remediation was required.
4.9. Telecommunication Infrastructure
Longwalls 22 to 24A have directly mined beneath approximately 19.1 kilometres of buried copper cable and 1.2 kilometres of buried optical fibre cable and 2.5 kilometres of aerial cable.
During the mining of Longwall 24A there was tilting of Telstra poles supporting the aerial cable network in the residential area of Tahmoor, around Courtland Avenue, Pandora Place, Tanya Place, Lintina Street and Mitchell Close. The movement of the poles created excess sag and tension within the aerial distribution network. Telstra, in consultation with the MSB, adjusted the cable tensions where necessary, to prevent loss of service, and where aerial cables crossed streets, hazard to traffic.
The areas requiring adjustment of the aerial cables were:
10 Pair second span east into Pandora Place, which were tight relative to other spans.
Lead-in to Nos 4 & 6 Tanya: No 4 was tight and required checking and No 6 ran through a tree in front yard.
Lead-in to No 9 Lintina was tight and required checking and adjustment.
2 x 10 Pair in Lintina, 3rd & 4th spans west from Courtland, 3rd span were loose and into two trees and 4th span cables were into one tree.
Lead-ins to No 8 & 10 Mitchell were tight and required checking and adjustment.
The major Inter Exchange Network optical fibre and main copper cables were not impacted by LW24A.
4.9.1. Exceedence of Defined Triggers
During the mining of Longwall 24A no triggers associated with the Management Plan for Longwall Mining (LW24 to LW25) Beneath Telstra Plant at Tahmoor and Thirlmere NSW were exceeded. Adjustments to aerial cables were carried out as required.
4.10. Inghams Infrastructure
4.10.1. Processing Plant
A joint between ground slabs within the Plant was observed to open up. The joint was sealed during mining and no further impacts were observed.
The Management Plan required a structural inspection and action plan to be developed if measured tilts of the High-Rise Freezer exceeded 2 mm/m tilt. This trigger level was not exceeded and no remediation work was necessary.
The most accurate measure of tilt is ground tilt between Plant Perimeter Marks 2 to 7. The survey results indicated a maximum tilt of approximately 0.69 mm/m after Longwall 24A, falling in an easterly direction towards the longwall face. This tilt contributed to correcting a tilt of approximately 0.5 mm/m which occurred in relation to previous mining in the area. This tilt is very small and is oriented in the expected direction.
Mine Subsidence Engineering Consultants 34 Xstrata Coal Tahmoor Colliery Report No. MSEC335 Longwall 24A January 2009 End of Panel Report Subsidence Monitoring Report
4.10.2. Inghams Dams
Due to the increased subsidence at the Inghams dams, the grade on an overflow pipe between two treatment plants was reversed. This pipe has been re-laid and no further remediation work is required.
4.10.3. Exceedence of Defined Triggers
During the mining of Longwall 24A triggers associated with the Tahmoor Colliery Inghams Enterprises Pty Ltd Surface Safety Serviceability and Management Plan (Rev K, March 2008) were exceeded.
Differential vertical movements exceeded the Blue trigger between survey marks Plant 11 and Plant 12, which are located on the southern side of the Carton Tunnel. The pegs are spaced approximately 21 metres apart and the corresponding ground tilt is therefore 0.5 mm/m. No impacts were observed.
The displacement sensor 2 exceeded the Blue trigger on numerous occasions but was found to be faulty and in need of adjustment or replacement. These exceedences are therefore not related to mining.
4.11. Residential Structures and Public Amenities
A register of observed impacts is based on claims received from the Mine Subsidence Board (MSB). Information on the nature of the impacts was provided by the MSB and Sunrise Property Building Services, who inspect impacted structures on behalf Tahmoor Colliery. The register was updated on a weekly basis and the statistics provided in this report are based on impacts recorded up to the week starting 24 August 2008, two days after the commencement of Longwall 24A.
Information on the nature of impacts to each structure has been collected in the following manner:
1. Initial details of claim as supplied by the MSB on a weekly basis
2. Photographs taken during claim inspections by the MSB
3. Site visits to selected properties in company with MSB representatives
4. Inspection contained in claim files held by the MSB
A summary of reported impacts following the completion of Longwall 24A is provided in Table 4-2. The count of residential structures and public amenities includes only those structures that were predicted to experience more than 20 mm of subsidence due to the extraction of Longwalls 22 to 24A.
Table 4-2 Summary of Observed Impacts to Structures
Total after
LWs 22 to 24A Increment
during LW 24A
Number of Structures within zone of influence (predicted subsidence > 20 mm)
1016 183
Number of properties with reported impacts (not including refused claims)
160 32
Number of properties with reported impacts that relate to main structures (e.g. house or shop)
147 31
Number of properties with reported impacts that only relate to associated structures
13 1
The above information can be misleading as the majority of claims received during the mining of Longwall 24A were associated with the previous mining of Longwalls 22 to 24B. This is due to time lag between the actual impact and the claim of an impact by residents to the Mine Subsidence Board.
This is illustrated by a spatial plot of locations of impacts reported during the mining of Longwall 24A in Figure 4.2. A total of 18 of 32 claims related to the mining of Longwalls 22 to 24B, rather than the active Longwall 24A.
Mine Subsidence Engineering Consultants 35 Xstrata Coal Tahmoor Colliery Report No. MSEC335 Longwall 24A January 2009 End of Panel Report Subsidence Monitoring Report
Figure 4.2 Locations of Impacts during the mining of Longwall 24A
Observed impacts have been classified in accordance with the impact classification tables provided in the SMP Report. Strain impacts are classified generally in accordance with Table C.1 of the Australian Standard AS2870 – 1996, although the classification was extended to include a Category 5, which corresponds to the Very Severe Damage Category of the UK National Coal Board Classification.
Australian Standards AS2870 advises that crack width is the main factor by which damage to walls is categorized. Predicted crack width was also the method by which impact assessments were conducted. Crack width has therefore been used for the purposes of classifying strain impacts to residential structures.
Predictions and impact assessments for residential structures and public amenities were provided in the SMP Report No. MSEC157. Predictions and assessments focussed on two separate types of subsidence movements: normal systematic subsidence movements and non-systematic movements. Detailed impact assessments were provided for each individual house on the basis that normal systematic movements would occur. The potential for impacts from non-systematic subsidence movements were discussed separately and no specific predictions were provided. Areas that are considered to have experienced non-systematic movements were identified in Section 2.2.
Mine Subsidence Engineering Consultants 36 Xstrata Coal Tahmoor Colliery Report No. MSEC335 Longwall 24A January 2009 End of Panel Report Subsidence Monitoring Report
4.11.1. Comparison in General
A comparison between observed and predicted impacts is provided in Table 4-3.
Table 4-3 Comparison between Observed and Predicted Impacts in General
Predicted Total No. of
Structures Observed Total No. of
Structures
Tilt Impacts
No impact to house or civil structure 0 869
Tilt Impact Category A 1008 systematic
+/- unspecified non-systematic 142
Tilt Impact Category B 8 systematic
+/- unspecified non-systematic 4
Tilt Impact Category C 0 systematic
+/- unspecified non-systematic 0
Tilt Impact Category D 0 systematic
+/- unspecified non-systematic 1
Total 1016 1016
Strain Impacts
No impact to house or civil structure 0 869
Strain Impact Category 0 524 systematic
+/- unspecified non-systematic 101
Strain Impact Category 1 465 systematic
+/- unspecified non-systematic 16
Strain Impact Category 2 27 systematic
+/- unspecified non-systematic 17
Strain Impact Category 3 0 systematic
+/- unspecified non-systematic 4
Strain Impact Category 4 0 systematic
+/- unspecified non-systematic 5
Strain Impact Category 5 0 systematic
+/- unspecified non-systematic 4
Total 1016 1016
Notes: “Systematic” refers to impacts assessed based on predictions of systematic subsidence movements, as described in Section 3.17.1.1 of SMP Report No. MSEC157. “non-systematic” refers to the predicted potential for impacts to structures from non-systematic subsidence movements, as described in Section 3.17.1.4 of SMP Report No. MSEC157.
A discussion of the above comparison is provided in Section 4.11.3.
Mine Subsidence Engineering Consultants 37 Xstrata Coal Tahmoor Colliery Report No. MSEC335 Longwall 24A January 2009 End of Panel Report Subsidence Monitoring Report
4.11.2. Comparison based on Predicted Impact Categories
A comparison has been made between observed and predicted impacts on a structure by structure basis for Strain Impacts only. The comparison is based on information up to 24 August 2008. A summary is provided in Table 4-4 below.
Table 4-4 Summary of Comparison between Observed and Predicted Impacts for each Structure
Strain Impact
Category
Total No. of Observed Impacts
for Structures predicted to be Strain Impact
Category 0
Total No. of Observed Impacts for Structures predicted to be Strain
Impact Category 1
Total No. of Observed Impacts for Structures predicted to be Strain
Impact Category 2
Total
No impact 476 373 20 869
Cat 0 28 68 5 101
Cat 1 7 8 1 16
Cat 2 6 10 1 17
Cat 3 2 2 0 4
Cat 4 3 2 0 5
Cat 5 2 2 0 4
Total 524 465 27 1016
% claim 9 % 20 % 26 % 14 %
% Obs > Pred
4 % 3 % 0 % -
% Obs <= Pred
96 % 97 % 100 % -
Note: Predicted impacts due to systematic subsidence only, as per Section 3.17.1.1 of SMP Report No. MSEC157.
4.11.3. Discussion of Results
Given that observed impacts are less than or equal to predicted impacts in 96 % of cases, it is considered that the current methods are generally conservative even though non-systematic movements were not taken into account in the predictions and assessments. However, when compared on a house by house basis, the predictions have been substantially exceeded in a small proportion of cases.
The majority, if not all, of the houses that have experienced Category 3, 4 or 5 impacts are considered to have experienced substantial non-systematic subsidence movements. The consideration is based on nearby ground survey results, where upsidence bumps are observed in subsidence profiles and high localised strain is observed. The potential for impact from non-systematic movements were discussed generally and not included in the specific impact assessments for each structure.
The inability to specify the number or probability of impacts due to the potential for non-systematic movements is a shortcoming of the current method. It is considered that there is significant room for improvement in this area and recommendations have been provided in a report following a review of predicted impacts on dwellings (Report No. MSEC361).
The comparison shows a favourable observation that the overall proportion of claims increased for increasing predicted impact categories. This suggests that the main parameters currently used to make impact assessments (namely predicted systematic curvature and maximum plan dimension of each structure) are credible.
Mine Subsidence Engineering Consultants 38 Xstrata Coal Tahmoor Colliery Report No. MSEC335 Longwall 24A January 2009 End of Panel Report Subsidence Monitoring Report
The overall claim rate for main structures during the mining of Longwalls 22 to 24A was 14%. The claim rate for main structures affected by subsidence due to the mining of Longwall 24A was 8%. The result is surprising given that observed subsidence substantially exceeded predictions.
Importantly, all structures have remained safe and serviceable throughout the mining period.
4.11.4. Swimming Pools
No impacts have been observed to swimming pools due to the mining of Longwall 24A.
4.11.5. Associated Structures
Minor impacts have been observed for 3 structures due to the mining of Longwall 24A.
4.11.6. Fences
The potential for impacts to fences was raised in the SMP Report and a total of 3 properties have claimed impacts to gates and properties above Longwall 24A.
4.11.7. Exceedence of Defined Triggers
During the mining of Longwall 24A one of the triggers associated with the Tahmoor Colliery Longwall 24 to 26, Residential Establishments Surface Safety Serviceability and Management Plan (Rev C, May 2008) was exceeded. The trigger exceeded was a ground tilt which exceeded 7 mm/m along Ralfe St between Pegs RF21 and RF23.
In response to the identification of the exceedence of the above trigger, visual inspections of nearby houses on Tanya Place were undertaken and no structural issues were found.
Impacts to one house were observed to be Category 4. A structural inspection was undertaken and the house was found to be safe and serviceable.
4.12. Public Amenities
A number of public amenity structures experienced mine subsidence movements due to the mining of Longwall 24A. All of the structures were located along Remembrance Drive. The majority of the structures comprise of relatively small shopfronts. The large shopping centre, Tahmoor Town Centre, also experienced subsidence movements and discussion is provided separately in Section 4.13.
Only one structure experienced impacts during mining. A construction joint in one shop on Remembrance Drive was observed to open to Category 3 width during the mining of Longwall 24A. A structural inspection was undertaken and the house was found to be safe and serviceable.
4.12.1. Exceedence of Defined Triggers
During the mining of Longwall 24A one of the triggers associated with the Tahmoor Colliery Longwall 24 to 26, Public Amenities, Surface Safety Serviceability and Management Plan (Rev C, May 2008) was exceeded. One shop experienced an opening of a construction joint. A structural inspection was undertaken and the house was found to be safe and serviceable.
4.13. Tahmoor Town Centre
During the mining of Longwall 24A cracking at the base of some columns within the basement car park at the Tahmoor Town Centre development was reported. John Matheson & Associates Pty Ltd undertook an investigation of these, to observe the cracks and to report on the history of the observed cracks and the likely causes.
4.13.1. Observations of Cracking
Cracking was evident in the columns before the commencement of active subsidence as outlined in the pre-mining inspection report prepared by Mr John Schwarz.
Following mining, a number of columns were observed to have cracking around the column base, where the concrete has been poured so that it bears directly upon the ground floor slab. The report found that it was evident that the concrete ground slab was cast before the concrete column and that the ovoid recess
Mine Subsidence Engineering Consultants 39 Xstrata Coal Tahmoor Colliery Report No. MSEC335 Longwall 24A January 2009 End of Panel Report Subsidence Monitoring Report
had been incorrectly located so that when casting the column, the cover concrete was cast directly onto the ground slab rather than wholly upon the underlying footing without any provision for differential movement between the ground slab and overlying column concrete. The intimate bearing of the column cover concrete on the ground slab has meant that restraint forces have been developed sufficient to cause slab cracking and surface spalling cracks at the base of the columns.
The connections between the concrete columns and the suspended concrete slab above were inspected and these connections appeared to be unchanged from earlier inspections and there was no discernable change in the condition of the structure in these locations.
4.13.2. Possible Causes of Cracking
The observed cracking appears to have been caused by restraint forces developed between the concrete column and the basement slab on ground. The restraint forces develop where the slab moves away from the column due to concrete shrinkage, significant slab shortening during extended periods of low temperature and tensile ground strains caused by mine subsidence.
From an analysis of crack size versus time overlaid with ambient temperature conditions and the progress of LW24A/B, the following was observed:
Prior to mining LW24B, 16 columns had pre-existing category 0 or 1 cracking.
During or after mining LW24B and prior to mining LW24A, 2 additional columns developed category 0/1 cracking and one column developed category 2 cracking.
During or after mining LW24A and prior to the extended cold period during winter 2008, 2 additional columns developed category 0/1 cracking and one column developed category 2 cracking.
Additional cracking appears not to have developed during the recent very cold period of weather.
4.13.3. Conclusions
It has been concluded that subsidence is the most likely cause of the additional 4 cracked columns and the growth in 2 columns from category 0/1 to category 2 although pre-existing ground slab shrinkage strains and poor column/ground slab construction detail may be contributing to the additional observed cracking.
The observed cracking appears to be localised within the column concrete cover zone and does not appear to propagate into the core of the column within the confinement of the column ties and longitudinal reinforcement. The columns were effectively designed as pinned at the base and therefore minor spalling cracking, whilst it is undesirable, is not considered to be seriously detrimental to the overall strength of the structure and that repairs may be carried out to control further cracking of category 1 cracking and epoxy concrete repairs to the small number of category 2 cracks observed.
Tahmoor Colliery has recently patched 20 columns within the TTC basement. The majority of the columns are located along Grid E. The patching works were undertaken to remove the existing spalling cracks from the reporting program so that the management plan can focus on the development of new structural cracking caused by subsidence. JMA reports that a number of construction defects were observed whilst making the repairs, which will improve concrete confinement, ductility and column shear strength.
4.13.4. Exceedence of Defined Triggers
During the mining of Longwall 24A no triggers associated with the Tahmoor Colliery Longwall 24 to 26, Tahmoor Town Centre, Surface Safety Serviceability and Management Plan (Rev D, August 2006) were exceeded.
No remediation works are required.
Mine Subsidence Engineering Consultants 40 Xstrata Coal Tahmoor Colliery Report No. MSEC335 Longwall 24A January 2009 End of Panel Report Subsidence Monitoring Report
CHAPTER 5. SUMMARY OF RESULTS
Observed subsidence, tilt and curvature due to the mining of Longwall 24A have substantially exceeded predictions. Maximum observed subsidence was 1169 mm, which was more than double the maximum predicted subsidence of 509 mm. While observed tilts and curvature were also substantially greater than predicted, observed ground strains were within the normal range.
The observation of increased subsidence was not observed at other nearby longwalls at Tahmoor Colliery, where there was a reasonable correlation between predicted and observed profiles over Longwalls 22, 23 and 24B.
Observed subsidence was greatest above the southern half of Longwall 24A, and gradually reduced in magnitude towards the northern half of the longwall, which was directly beneath the urban area of Tahmoor.
The nature and magnitude of the increased subsidence is rare and the cause of the increased subsidence is currently not known. Tahmoor Colliery has commissioned a geotechnical study by Dr Winton Gale of Strata Control Technology to try to identify the cause or causes of the increased subsidence. Results of this study are not yet available as research is continuing. Once it became apparent that increased subsidence had developed, Tahmoor Colliery revised its management plans during extraction of LW24A to manage potential increased impacts to surface infrastructure before the longwall extracted beneath the urban area of Tahmoor.
While subsidence was substantially exceeded predictions in most locations, there remains a reasonable correlation between observed and predicted impacts, particularly in relation to public infrastructure such as sewer mains, water mains, gas mains, and electrical and telecommunications infrastructure. Impacts to road pavements were similar in frequency compared to those observed during the mining of previous longwalls. The impacts to the road pavement on Lintina Street were, however, more severe than had been observed previously.
In relation to structures, the overall claim rate for main structures during the mining of Longwalls 22 to 24A was 14%. The claim rate for main structures affected by subsidence due to the mining of Longwall 24A was 8%. The result is surprising given that observed subsidence substantially exceeded predictions.
Given that observed impacts to structures are less than or equal to predicted impacts in 96 % of cases, it is considered that the current methods are generally conservative even though non-systematic movements were not taken into account in the predictions and assessments. However, when compared on a house by house basis, the predictions have been substantially exceeded in a small proportion of cases.
Importantly, all structures have remained safe and serviceable throughout the mining period.
In relation to the Bargo Gorge, the monitoring results indicate that no measureable upsidence or closure has occurred across any of the monitoring lines across the Bargo Gorge during the mining of Longwall 24A. All differential movements have been very small and close to or within stated survey tolerance. The current observed movements during the mining of Longwall 24A are less than the predicted Longwall 24A maximum incremental upsidence of 20 mm and maximum incremental closure of 50 mm. Given the incised nature of the Gorge and its significant valley height, it was considered possible that actual upsidence and closure movements might exceed predictions but this does not appear to have occurred.
No physical, hydrological or water quality impacts were observed to the Bargo River. Four very minor rockfalls have been observed during mining, though each of these has been observed following significant rainfall or wind events. A geotechnical inspection of the rockfalls found no evidence to show that mining activity is directly responsible for any of the four rock falls and hence a mining associated trigger is considered unlikely. Given the unstable nature of cliffs, it is very difficult to know whether mine subsidence has contributed to these very minor rockfalls. However, given that no upsidence or closure is apparent across any of the monitoring lines, it is considered that any contribution from mining would be very small.
Mine Subsidence Engineering Consultants 41 Xstrata Coal Tahmoor Colliery Report No. MSEC335 Longwall 24A January 2009 End of Panel Report Subsidence Monitoring Report
APPENDIX A. FIGURES AND DRAWINGS
Mine Subsidence Engineering Consultants Fig. MSEC335-01 Rev ?
0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160 170 180 190 200 210Distance along Bradbury Street Line from Survey Mark BR1 (m)
-2.0
-1.5
-1.0
-0.5
0.0
0.5
1.0
1.5
2.0
Str
ain
(mm
/m)
-3
-2
-1
0
1
2
3
Tilt
(m
m/m
)
100908070605040302010
0-10
Sub
side
nce
(mm
)
During LW23
Latest Survey (End of LW24A)
Predicted Profiles
266
268
270
272
274
276
Sur
face
Lev
el A
HD
(m
)
BR1BR2
BR3BR4
BR5 BR6BR7
BR8BR9
BR10
Tahmoor Colliery - Total Subsidence Profilesalong Bradbury Street Line
Nominal Survey Toleranceof ± 0.25 mm/m
over 20 m bay lengths
I:\Projects\Tahmoor\SurveyData\Bradbury Street\Bradbury (LW24A EOP).grf
LW22
LW23A
LW24A
LW24B
Mine Subsidence Engineering Consultants Fig. MSEC335-02 Rev ?
0 50 100 150 200 250 300 350 400 450 500Distance along BC Line from Survey Mark Dam11 (m)
-2.0
-1.5
-1.0
-0.5
0.0
0.5
1.0
1.5
2.0
Str
ain
(mm
/m)
LW 24A
-6-5-4-3-2-10123456
Tilt
(m
m/m
)
1000
900
800
700
600
500
400
300
200
100
0
Sub
side
nce
(mm
)
During LW24A
Survey on 19-Mar-08
Survey on 22-Apr-08
Latest Survey
Predicted Profiles
250
255
260
265
270
275
280
285
Sur
face
Lev
el A
HD
(m
)
LW 24A
Dam
11
Dam
12
Da
m1
3
Da
m1
4
Dam
15
Dam
16
Dam
17
Dam
18
Dam
19
HR
F6
HR
F5
BC
1
BC
2
BC
3
BC
4
BC
5
BC
6
BC
7
RF
15
RF
16
RF
17
RF
18
RF
19
Tahmoor Colliery - Total Subsidence Profilesalong BC Line
Nominal Survey Toleranceof ± 0.25 mm/m
over 20 m bay lengths
I:\Projects\Tahmoor\SurveyData\Inghams\BC Line (LW24A EOP).grf
Monitoring line changesdirection at Pegs HRF5,RF15 and RF16
Estimate Peg HRF6 subsided80 mm at time of initial survey
Estimated subsidence for Pegs BC1 to BC7 at time of initial survey
LW22
LW23A
LW24A
LW24B
Mine Subsidence Engineering Consultants Fig. MSEC335-03 Rev ?
0 100 200 300 400 500 600 700 800 900 1000 1100 1200 1300 1400Distance along Castlereagh Street Line from Survey Mark C1 (m)
-3.5
-3.0
-2.5
-2.0
-1.5
-1.0
-0.5
0.0
0.5
1.0
Str
ain
(mm
/m)
LW 22 LW 23 LW 24B
-6-5-4-3-2-1012345
Tilt
(m
m/m
)
650600550500450400350300250200150100
500
Sub
side
nce
(mm
)
During LW22
During LW23
During LW24B
Latest Survey (End of LW24A)
Predicted Profiles
264
266
268
270
272
274
276
278
280
282
284
Sur
face
Lev
el A
HD
(m
)
LW 22 LW 23 LW 24B
264.3
C1 C6
C11
C16 C21
C26 C31C36 C41
C46
C51
C56
C61
Pegs lost and replacedprior to start of LW24B
PotentialHidden Creek
PotentialHidden Creek
PotentialHidden Creek
Change inLine Direction
Reduced subsidenceafter LW22. Additionalsubsidence during LW23.
Break in Line acrossThirlmere Way
PotentialHidden Creek
Survey discontinuity
Survey discontinuity
Tahmoor Colliery - Total Subsidence Profilesalong Castlereagh Street
Change inLine Direction
Change inLine Direction
Break in Line across
Thirlmere Way
Subsidencegreater thanpredicted
Systematic Compressive
Strain
MyrtleCreek
Anomaly
Nominal Survey Toleranceof ± 0.25 mm/m
over 20m bay lengthsSystematic
CompressiveStrain
(Roadworks)
I:\Projects\Tahmoor\SurveyData\Castlereagh Street\Castlereagh (LW24A EOP).grf
LW22
LW23A
LW24A
LW24B
Tahmoor Colliery - Total Subsidence Profilesalong Chapman Street Line
Mine Subsidence Engineering Consultants Fig. MSEC335-04 Rev ?
0 50 100 150 200 250 300 350 400 450 500 550Distance along Chapman Street Line from Survey Mark CH1 (m)
-3.0
-2.5
-2.0
-1.5
-1.0
-0.5
0.0
0.5
1.0
Str
ain
(mm
/m)
LW 23 (not surveyed) LW 24B
-5
-4
-3
-2
-1
0
1
2
3
4
Tilt
(m
m/m
)
600
500
400
300
200
100
0
Sub
side
nce
(mm
)
During LW 24B
Latest Survey (End of LW24A)
Predicted Profiles
270
272
274
276
278
280
282
284
286
288
Sur
face
Lev
el A
HD
(m
)
LW 23 (not surveyed) LW 24B
270.5
CH1 CH2 CH3 CH4 CH5 CH6 CH7 CH8 CH9 CH10CH11
CH12CH13
CH14CH15
CH16CH17
CH18CH19
CH20
CH21CH22
CH23
Nominal Survey Toleranceof ± 0.25 mm/m
over 20m bay lengths
I:\Projects\Tahmoor\SurveyData\Chapman Street\Chapman (LW24A EOP).grf
Closest peg to Railway
LW22
LW23A
LW24A
LW24B
Mine Subsidence Engineering Consultants Fig. MSEC335-05 Rev ?
0 50 100 150 200 250 300 350Distance along Line from Survey Mark RF21 (m)
-2.0
-1.5
-1.0
-0.5
0.0
0.5
1.0
1.5
2.0
Str
ain
(mm
/m)
LW 24A LW 25
-7
-6
-5
-4
-3
-2
-1
0
1
2
3
Tilt
(m
m/m
)
900
800
700
600
500
400
300
200
100
0
Sub
side
nce
(mm
)
During LW24A
Latest Survey
Predicted Profiles
260
265
270
275
280
285
290
Sur
face
Lev
el A
HD
(m
)
LW 24A LW 25
RF
21
CL1 CL2 CL3 CL
4
CL
5
CL6
CL
7
CL8
CL9
CL
10
CL
11
CL1
2
CL1
3
CL
14
Tahmoor Colliery - Total Subsidence Profilesalong Courtland Avenue
Nominal Survey Toleranceof ± 0.25 mm/m
over 20 m bay lengths
I:\Projects\Tahmoor\SurveyData\Courtland Avenue\Courtland Ave (LW24A EOP).grf
Estimated subsidencefor Pegs CL1 to CL14
LW22
LW23A
LW24A
LW24B
Mine Subsidence Engineering Consultants Fig. MSEC335-06 Rev ?
0 10 20 30 40 50 60 70 80 90 100 110 120 130 140Distance along Line from Survey Mark R24 (m)
-2.0
-1.5
-1.0
-0.5
0.0
0.5
1.0
1.5
2.0
Str
ain
(mm
/m)
-3
-2
-1
0
1
2
3
Tilt
(m
m/m
)
140
120
100
80
60
40
20
0
Sub
side
nce
(mm
)
During LW24A
Latest Survey
Predicted Profiles
255
260
265
270
275
280
285
Sur
face
Lev
el A
HD
(m
)
R24
ET
1
ET
2
ET
3
ET
4
ET
5
ET
6
Tahmoor Colliery - Total Subsidence Profilesalong Emmett Street
Nominal Survey Toleranceof ± 0.25 mm/m
over 20 m bay lengths
I:\Projects\Tahmoor\SurveyData\Emmett Street\Emmett St (LW24A EOP).grf
Estimated subsidencefor Pegs ET1 to ET6
LW22
LW23A
LW24A
LW24B
Mine Subsidence Engineering Consultants Fig. MSEC335-07 Rev ?
0 20 40 60 80 100 120 140 160 180 200 220 240 260Distance along Line from Survey Mark R14 (m)
-2.0
-1.5
-1.0
-0.5
0.0
0.5
1.0
1.5
2.0
Str
ain
(mm
/m)
LW 24A
-3
-2
-1
0
1
2
3
Tilt
(m
m/m
)
200
180
160
140
120
100
80
60
40
20
0
Sub
side
nce
(mm
)
During LW24A
Latest Survey
Predicted Profiles
255
260
265
270
275
280
285
Sur
face
Lev
el A
HD
(m
)
LW 24A
R1
4
L1 L2 L3 L4
L5 L6
L7 L8
L9
L10
L11
L12
Tahmoor Colliery - Total Subsidence Profilesalong Larkin Street
Nominal Survey Toleranceof ± 0.25 mm/m
over 20 m bay lengths
I:\Projects\Tahmoor\SurveyData\Larkin Street\Larkin St (LW24A EOP).grf
Estimated subsidencefor Pegs L1 to L12
LW22
LW23A
LW24A
LW24B
Mine Subsidence Engineering Consultants Fig. MSEC335-08 Rev ?
0 20 40 60 80 100 120 140 160 180 200 220 240 260 280Distance along Line from Survey Mark LA1 (m)
-2.0
-1.5
-1.0
-0.5
0.0
0.5
1.0
1.5
2.0
Str
ain
(mm
/m)
LW 24A
-4
-3
-2
-1
0
1
2
3
4
Tilt
(m
m/m
)
800
700
600
500
400
300
200
100
0
Sub
side
nce
(mm
)
During LW24A
Latest Survey
Predicted Profiles
260
265
270
275
280
285
290
Sur
face
Lev
el A
HD
(m
)
LW 24A
LA
1
LA
2
LA
3
LA4
LA5
LA
6
LA7
LA
8
LA
9
LA1
0
LA11
LA
12
LA13
Tahmoor Colliery - Total Subsidence Profilesalong Lintina Street
Nominal Survey Toleranceof ± 0.25 mm/m
over 20 m bay lengths
I:\Projects\Tahmoor\SurveyData\Lintina Street\Lintina Street (LW24A EOP).grf
Estimated subsidencefor Pegs LA1 to LA13
LW22
LW23A
LW24A
LW24B
Mine Subsidence Engineering Consultants Fig. MSEC335-09 Rev ?
0 50 100 150 200 250 300 350 400 450 500Distance along LW25 Draw Line from Survey Mark 24-1 (m)
-2.0
-1.5
-1.0
-0.5
0.0
0.5
1.0
1.5
2.0
Str
ain
(mm
/m)
LW 24A
-4
-2
0
2
4
6
8
10
12
Tilt
(m
m/m
)
11001000
900800700600500400300200100
0
Sub
side
nce
(mm
)
During LW24A
Latest Survey
Predicted Profiles
250
255
260
265
270
275
280
285
Sur
face
Lev
el A
HD
(m
)
LW 24A
24-1 2
4-2
24-
3
24-
4 24-
5
24-
6
24-
7
24-8
24-
9
24-1
0
24-
11
24-1
2
24-1
3
24-1
4
24-1
5
24-1
6
24-
17
24-
18
24-
19
Tahmoor Colliery - Total Subsidence Profilesalong LW24A Draw Line
Nominal Survey Toleranceof ± 0.25 mm/m
over 20 m bay lengths
I:\Projects\Tahmoor\SurveyData\LW24A Draw Line\LW24A Draw Line (LW24A EOP).grf
LW22
LW23A
LW24A
LW24B
Mine Subsidence Engineering Consultants Fig. MSEC335-10 Rev ?
0 20 40 60 80 100 120 140 160 180 200 220 240 260 280 300 320 340 360Distance along LW25 Draw Line from Survey Mark 25-1 (m)
-2.0
-1.5
-1.0
-0.5
0.0
0.5
1.0
1.5
2.0
Str
ain
(mm
/m)
-3
-2
-1
0
1
2
3
Tilt
(m
m/m
)
50
40
30
20
10
0
-10
Sub
side
nce
(mm
)
During LW24A
Latest Survey
Predicted Profiles
250
255
260
265
270
275
280
285
Sur
face
Lev
el A
HD
(m
)
25-
1 25-2 25
-3 25-4 25-
5
25-6
25-
7
25-8 25-
9 25-1
0
25-
11 25-
12 25-1
3
25-1
4
25-
15
25-1
6
Tahmoor Colliery - Total Subsidence Profilesalong LW25 Draw Line
Nominal Survey Toleranceof ± 0.25 mm/m
over 20 m bay lengths
I:\Projects\Tahmoor\SurveyData\LW25 Draw Line\LW25 Draw Line (LW24A EOP).grf
LW22
LW23A
LW24A
LW24B
Mine Subsidence Engineering Consultants Fig. MSEC335-11 Rev ?
0 50 100 150 200 250 300 350 400Distance along LW26 Draw Line from Survey Mark 26-1 (m)
-2.0
-1.5
-1.0
-0.5
0.0
0.5
1.0
1.5
2.0
Str
ain
(mm
/m)
LW26
-3
-2
-1
0
1
2
3
Tilt
(m
m/m
)
60
50
40
30
20
10
0
-10
-20
Sub
side
nce
(mm
)
During LW24A
Latest Survey
Predicted Profiles
240
245
250
255
260
265
270
Sur
face
Lev
el A
HD
(m
)
LW26
26-1
26-2
26-3
26-426-5
26-6
26-7
26-826-9 26-10 26-11 26-12 26-13 26-14 26-15
26-1626-17 26-18
Tahmoor Colliery - Total Subsidence Profilesalong LW26 Draw Line
Nominal Survey Toleranceof ± 0.25 mm/m
over 20 m bay lengths
I:\Projects\Tahmoor\SurveyData\LW26 Draw Line\LW26 Draw Line (LW24A EOP).grf
Mine Subsidence Engineering Consultants Fig. MSEC335-12 Rev ?
93.6 93.7 93.8 93.9 94.0 94.1 94.2 94.3 94.4 94.5 94.6 94.7 94.8 94.9 95.0 95.1 95.2 95.3Chainage along Main Southern Railway (km)
-2.0
-1.5
-1.0
-0.5
0.0
0.5
1.0
Str
ain
(mm
/m)
LW 25 LW 22LW 23LW 24BLW 25
-2
-1
0
1
2
Tilt
(m
m/m
)
140
120
100
80
60
40
20
0
Sub
side
nce
(mm
)
During LW 22
During LW 23
During LW 24B
During LW 24A
Latest Survey
Predicted Profiles
260
262
264
266
268
270
272
274
276
278
280
Sur
face
Lev
el A
HD
(m
)
LW 22LW 23LW 24BLW 25
Projectionof Dyke
93.600 93.700
93.800
93.90094.000 94.100
94.20094.300
94.400 94.500 94.600 94.700
94.80094.900 95.000
95.100 95.200 95.300
Thirlmere WayOverbridge Tahmoor
RailwayStation
Creek CreekCreek
MyrtleCreek
SewerSewer Water
Main
Gas
Gas
Culvert94.707
Culvert94.576
Culvert94.225
Culvert93.750
Pegs identified as disturbedby surveyor prior to start of LW24B
Survey discontinuity Reduced subsidenceduring LW22
Tahmoor Colliery - Total Subsidence Profilesalong Main Southern Railway Corridor Line
Upsidence
Upsidence
Valley ClosureIncreasing
during LW 24A
Bump
Pegs lost in week starting 7 Jan 2007 due to rail maintenance activities.Replaced 31 Oct 2007.
Datum check: extra 16mmfrom 21-Nov-06 to 30-Jan-07
Affected byvehicle loads
Nominal Survey Toleranceof ± 0.25 mm/m
over 20m bay lengths
Bumped peg at entranceto rail corridor. No change.
Bumped peg at entranceto rail corridor
Bumped peg.No change since
first survey of LW24A.
Bumped peg.No change since
first survey of LW24A.
Strains increasingduring LW24A.
I:\Projects\Tahmoor\SurveyData\Main Southern Railway\Railway Line\Main Southern Railway Total (LW24A EOP).grf
LW22
LW23A
LW23B
LW24A
LW24B
92.0 km
93.5 km
94.0 km
94.5 km
95.0 km
95.5 km
92.5 km
93.0 km
Overbridge
Culvert
Mine Subsidence Engineering Consultants Fig. MSEC335-13 Rev ?
93.6 93.7 93.8 93.9 94.0 94.1 94.2 94.3 94.4 94.5 94.6 94.7 94.8 94.9 95.0 95.1 95.2 95.3Chainage along Main Southern Railway (km)
-2.0
-1.5
-1.0
-0.5
0.0
0.5
1.0
Str
ain
(mm
/m)
LW 25 LW 22LW 23LW 24BLW 25
-2
-1
0
1
2
Tilt
(m
m/m
)
100
80
60
40
20
0
Sub
side
nce
(mm
)
During LW 24A
Latest survey
Predicted Profiles
260
262
264
266
268
270
272
274
276
278
280
Sur
face
Lev
el A
HD
(m
)
LW 22LW 23LW 24BLW 25
Projectionof Dyke
93.600 93.700
93.800
93.90094.000 94.100
94.20094.300
94.400 94.500 94.600 94.700
94.80094.900 95.000
95.100 95.200 95.300
Thirlmere WayOverbridge Tahmoor
RailwayStation
Creek CreekCreek
MyrtleCreek
SewerSewer Water
Main
Gas
Culvert94.707
Culvert94.576
Culvert94.225
Culvert93.750
Tahmoor Colliery - Incremental Subsidence ProfilesMain Southern Railway Corridor Line during LW24A
Nominal Survey Toleranceof ± 0.25 mm/m
over 20m bay lengths
Negligible change since first survey.Subsidence bumps likely to be due to
corridor activity October 2007.
Bumped peg.No change since
first survey.
NOTE: Concrete sleepers installed on both Up and Dn Mainsbetween LW 24B and 24A. Expansion switch and free rail in operation as part of Tahmoor Switch Trial.
Bumped peg.No change since
first survey.
Bumped peg at entranceto rail corridor
Bumped peg at entranceto rail corridor
Bumped peg at entranceto rail corridor
Strain growth atcreek. This site haspreviously seencompressive strain.
Possible strain growth. This site has previouslyseen compressive strain.
LW22
LW23A
LW23B
LW24A
LW24B
92.0 km
93.5 km
94.0 km
94.5 km
95.0 km
95.5 km
92.5 km
93.0 km
Overbridge
Culvert
I:\Projects\Tahmoor\SurveyData\Main Southern Railway\Railway Line\Main Southern Railway Inc (LW24A EOP).grf
Mine Subsidence Engineering Consultants Fig. MSEC335-14 Rev ?
240 220 200 180 160 140 120 100 80 60 40 20 0Distance along Mitchell Cl Line from Survey Mark LA8 (m)
-5.0-4.5-4.0-3.5-3.0-2.5-2.0-1.5-1.0-0.50.00.51.0
Str
ain
(mm
/m)
LW 24A
-5
-4
-3
-2
-1
0
1
2
3
Tilt
(m
m/m
)
500
450
400
350
300
250
200
150
100
50
0
Sub
side
nce
(mm
)
During LW24A
Latest Survey
Predicted Profiles
266
268
270
272
274
276
278
280
Sur
face
Lev
el A
HD
(m
)
LW 24A
LA8
ML
1
ML2
ML3
ML4
ML5
ML6
ML7
ML8
ML
9
ML1
0
ML1
1
Tahmoor Colliery - Total Subsidence Profilesalong Mitchell Close during LW24A
Nominal Survey Toleranceof ± 0.25 mm/m
over 20 m bay lengths
I:\Projects\Tahmoor\SurveyData\Mitchell Close\Mitchell Cl (LW24A EOP).grf
Estimated subsidencefor Pegs ML1 to ML11
Cracks in pavement atlocation of elevatedground strain.
LW22
LW23A
LW24A
LW24B
Mine Subsidence Engineering Consultants Fig. MSEC335-15 Rev ?
0 50 100 150 200 250Distance along Pandora Pl Line from Survey Mark PA1 (m)
-2.0
-1.5
-1.0
-0.5
0.0
0.5
1.0
1.5
2.0
Str
ain
(mm
/m)
LW 24A LW 25
-3
-2
-1
0
1
2
3
Tilt
(m
m/m
)
200
180
160
140
120
100
80
60
40
20
0
Sub
side
nce
(mm
)
During LW24A
Latest Survey
Predicted Profiles
265
270
275
280
285
290
295
Sur
face
Lev
el A
HD
(m
)
LW 24A LW 25
PA
1 PA
2
PA
3
PA
4
PA
5
PA
6
PA
7
PA
8
PA
9
PA
10
PA
11
PG
16
Tahmoor Colliery - Total Subsidence Profilesalong Pandora Place
Nominal Survey Toleranceof ± 0.25 mm/m
over 20 m bay lengths
I:\Projects\Tahmoor\SurveyData\Pandora Place\Pandora Pl (LW24A EOP).grf
Estimated subsidencefor Pegs PA1 to PA11
LW22
LW23A
LW24A
LW24B
Mine Subsidence Engineering Consultants Fig. MSEC335-16 Rev ?
0 50 100 150 200 250 300 350 400 450 500 550 600 650 700 750 800 850 900Distance along Line from Survey Mark 25-17 (m)
-2.0
-1.5
-1.0
-0.5
0.0
0.5
1.0
1.5
2.0
Str
ain
(mm
/m)
LW 25
-3
-2
-1
0
1
2
3
Tilt
(m
m/m
)
150
100
50
0
-50
Sub
side
nce
(mm
)
During LW24B
During LW24A
Latest Survey
260
265
270
275
280
285
290
295
Sur
face
Lev
el A
HD
(m
)
LW 25
PG
1P
G2
PG
3
PG
4
PG
5
PG
6
PG
7 PG
8
PG
9
PG
10
PG
11P
G12
PG
13P
G14
PG
15
PG
16P
G17
PG
18P
G19
PG
20
PG
21
BO
LT
5
BO
LT
4
BO
LT
3
BO
LT2
BO
LT
1
GA
TE
Tahmoor Colliery - Total Subsidence Profilesalong Progress Street
Nominal Survey Toleranceof ± 0.25 mm/m
over 20 m bay lengths
I:\Projects\Tahmoor\SurveyData\Progress Street\Progress Total (LW24A EOP).grf
LW22
LW23A
LW24A
LW24B
Strain not measured beyond PG21
Tilts over 60m bays,not standard 20m bays
Connect to High-RiseFreezer Line
Connect toRalfe St Line
Connect toPandora Pl Line
Change inline direction
Suspect many PG pegs have been disturbed verticallyby vehicle loads since installation in October 2006.
Damaged peg, reinstated priorto start of LW 25.
Connect toAbelia St Line
Connect toCourtland Ave Line
Connect toRemembrance Dr Line
Mine Subsidence Engineering Consultants Fig. MSEC335-17 Rev ?
0 50 100 150 200 250 300 350 400 450 500 550 600 650 700 750 800 850 900Distance along Line from Survey Mark 25-17 (m)
-2.0
-1.5
-1.0
-0.5
0.0
0.5
1.0
1.5
2.0
Str
ain
(mm
/m)
LW 25
-4
-3
-2
-1
0
1
2
3
4
5
6
Tilt
(m
m/m
)
70
60
50
40
30
20
10
0
-10
Sub
side
nce
(mm
)
During LW24A
Latest Survey
260
265
270
275
280
285
290
295
Sur
face
Lev
el A
HD
(m
)
LW 25
PG
1P
G2
PG
3
PG
4
PG
5
PG
6
PG
7 PG
8
PG
9
PG
10
PG
11P
G12
PG
13P
G14
PG
15
PG
16P
G17
PG
18P
G19
PG
20
PG
21
BO
LT
5
BO
LT
4
BO
LT
3
BO
LT2
BO
LT
1
GA
TE
Tahmoor Colliery - Incremental Subsidence Profilesalong Progress Street during LW24A
Nominal Survey Toleranceof ± 0.25 mm/m
over 20 m bay lengths
I:\Projects\Tahmoor\SurveyData\Progress Street\Progress Inc (LW24A EOP).grf
LW22
LW23A
LW24A
LW24B
Strains not measured beyond PG21
Tilts over 60m bays,not standard 20m bays
Connect to High-RiseFreezer Line
Connect toRalfe St Line
Connect toPandora Pl Line
Change inline direction
Damaged peg, reinstated priorto start of LW 25.
Connect toAbelia St Line
Connect toCourtland Ave Line
Connect toRemembrance Dr Line
Mine Subsidence Engineering Consultants Fig. MSEC335-18 Rev ?
0 50 100 150 200 250 300 350 400 450 500 550 600 650 700 750Distance along BC Line from Survey Mark Dam11 (m)
-3.5-3.0-2.5-2.0-1.5-1.0-0.50.00.51.01.52.0
Str
ain
(mm
/m)
LW 24A LW 25
-10
-8
-6
-4
-2
0
2
4
6
8
10
Tilt
(m
m/m
)
1000
900
800
700
600
500
400
300
200
100
0
Sub
side
nce
(mm
)
Survey on 10-Apr-08
During LW24A
Latest Survey
Predicted Profiles
260
265
270
275
280
285
290
Sur
face
Lev
el A
HD
(m
)
LW 24A LW 25
CP
12
RF
1
RF
2
RF
3
RF
4
RF
5
RF
6
RF
7
RF
8
RF
9
RF
10
RF
11
RF
12
RF
13
RF
14
RF
15
RF
16
RF
17
RF
18
RF
19
RF
20
RF
21
RF
22
RF
23
RF
24
RF
25
RF
26
RF
27
RF
28
RF
29
RF
30
PG
21
Tahmoor Colliery - Total Subsidence Profilesalong Ralfe Street
Nominal Survey Toleranceof ± 0.25 mm/m
over 20 m bay lengths
I:\Projects\Tahmoor\SurveyData\Ralfe Street\Ralfe Street (LW24A EOP).grf
Estimated subsidencefor Pegs RF1 to RF30
LW22
LW23A
LW24A
LW24B
Mine Subsidence Engineering Consultants Fig. MSEC335-19 Rev ?
0 100 200 300 400 500 600 700 800 900 1000Distance along Remembrance Drive Line from Survey Mark R36 (m)
-2.0
-1.5
-1.0
-0.5
0.0
0.5
1.0
1.5
2.0
Str
ain
(mm
/m)
LW 24A LW 25
-5
-4
-3
-2
-1
0
1
2
3
4
5
Tilt
(m
m/m
)
300
250
200
150
100
50
0
Sub
side
nce
(mm
)
During LW22
During LW23A&B
During LW24B
During LW24A
Latest Survey
Predicted Profiles
255
260
265
270
275
280
285
Sur
face
Lev
el A
HD
(m
)
LW 24A LW 25
R36
R34
R32 R30 R28
R26 R24 R22 R20 R18 R1
6
R14
R12
R10 R8 R6 R4
R2
RE
1
RE
3
RE
5
RE
7
RE
9
RE
11
Tahmoor Colliery - Total Subsidence Profilesalong Remembrance Drive Line
Nominal Survey Toleranceof ± 0.25 mm/m
over 20 m bay lengths
I:\Projects\Tahmoor\SurveyData\Remembrance Drive\Remembrance Total (LW24A EOP).grf
LW22
LW23A
LW24A
LW24B
Mine Subsidence Engineering Consultants Fig. MSEC335-20 Rev ?0 100 200 300 400 500 600 700 800 900 1000
Distance along Remembrance Drive Line from Survey Mark R36 (m)
-0.4
-0.2
0.0
0.2
0.4
Cur
vatu
re (
1/km
)
LW 24A LW 25
-2.0
-1.5
-1.0
-0.5
0.0
0.5
1.0
1.5
2.0
Str
ain
(mm
/m)
-8
-6
-4
-2
0
2
4
6
8
Tilt
(m
m/m
)
500
400
300
200
100
0
-100
Sub
side
nce
(mm
)
During LW24A
Latest Survey
Projected Profiles based on High-Rise Freezer surveys
Predicted Profiles in SMP Report (MSEC157)
255
260
265
270
275
280
285
Sur
face
Lev
el A
HD
(m
)
LW 24A LW 25
R36
R34
R32 R30
R28
R26 R24 R22 R20
R18 R16
R14
R12
R10 R8 R6 R4
R2
RE
1
RE
3
RE
5
RE
7
RE
9
RE
11
Tahmoor Colliery - Incremental Subsidence Profilesalong Remembrance Drive due to LW24A
Irregularity in subsidence profileconsistent between surveys andnot increasing. Suspect damageto survey pegs. Check next survey.
Bump increased this survey.No noticeable increase inground strain. Bump in line with impacts on Lintina Street.Check next survey.
I:\Projects\Tahmoor\SurveyData\Remembrance Drive\Remembrance Inc (LW24A EOP).grf
LW22
LW23A
LW24A
LW24B
Mine Subsidence Engineering Consultants Fig. MSEC335-21 Rev ?
-20 0 20 40 60 80 100 120 140 160 180 200 220 240 260 280 300 320Distance along line from Survey Mark SH13 (m)
-0.2
-0.1
0.0
0.1
0.2
0.3
0.4
0.5
Cur
vatu
re (
km-1)
LW 24A
-5
-4
-3
-2
-1
0
1
2
3
4
5
Tilt
(m
m/m
)
300
250
200
150
100
50
0
Sub
side
nce
(mm
)
Latest Survey
Observed LW24A profile pluspredicted normal LW25 (MSEC157)
Observed LW24A profile plusprojected LW25 (based on HRF LW24A)
260
265
270
275
280
285
290
Sur
face
Lev
el A
HD
(m
)
LW 24A
B03a B04 B05 B06a B06b B06c B07 B59a
B60a
B61a B62aB63a
B64a
B65aB66a Y01a Y02c
SH
13
SH
12
SH
11
SH
10
SH
9
SH
8
SH
7
SH
6
SH
5
SH
4
SH
3S
H2
SH
1
SH
14
SH
15
SH
16S
H1
7
SH
18
SH
19
SH
20
SH
21
Tahmoor Colliery - Total Subsidence Profilesalong Remembrance Drive Shopfronts
Tilt Trigger in Subsidence Management Plan
I:\Projects\Tahmoor\SurveyData\Remembrance Drive\Shopfronts\Shopfronts (LW24A EOP).grf
Estimated subsidence for PegsSH1 to SH13 at initial survey
Larkin St
Estimated subsidence for PegsSH14 to SH21 after LW24A
No.
155
No.
153
No.
151
No.
14
9
No.
14
7
No.
14
5
No.
14
3
No.
14
1
No.
13
9
No.
13
5-1
37
No.
13
1-1
33
No.
12
9
No.
12
5-1
27
No.
12
3
No.
12
1
No.
11
9
No.
11
9
Tilt Trigger in Subsidence Management Plan
Estimated tilt forPegs SH14 to SH21
after LW24A
Estimated curvature forPegs SH14 to SH21
after LW24A
LW22
LW23A
LW24A
LW24B
Mine Subsidence Engineering Consultants Fig. MSEC335-22 Rev ?
0 10 20 30 40 50 60 70 80 90 100 110Distance along Line from Survey Mark TA1 (m)
-2.0
-1.5
-1.0
-0.5
0.0
0.5
1.0
1.5
2.0
Str
ain
(mm
/m)
LW 24A LW 25
-7
-6
-5
-4
-3
-2
-1
0
1
2
Tilt
(m
m/m
)
600
500
400
300
200
100
0
Sub
side
nce
(mm
)
During LW24A
Latest Survey
Predicted Profiles
250
255
260
265
270
275
280
285
290
Sur
face
Lev
el A
HD
(m
)
LW 24A LW 25
TA
1
TA
2
TA
3
TA
4
TA
5
TA
6
Tahmoor Colliery - Total Subsidence Profilesalong Tanya Place
Nominal Survey Toleranceof ± 0.25 mm/m
over 20 m bay lengths
I:\Projects\Tahmoor\SurveyData\Tanya Place\Tanya Pl (LW24A EOP).grf
Estimated subsidencefor Pegs TA1 to TA6
LW22
LW23A
LW24A
LW24B
LW25
LW26
18-Nov
559 m
Tahmoor Colliery - Total Subsidence Profilesalong Thirlmere Way Line
Mine Subsidence Engineering Consultants Fig. MSEC335-23 Rev ?
0 200 400 600 800 1000 1200 1400 1600 1800Distance along Thirlmere Way Line from Survey Mark T1 (m)
-3.0
-2.0
-1.0
0.0
1.0
2.0
3.0
Str
ain
(mm
/m)
LW 22 LW 23A LW 24B LW 25
-4
-3
-2
-1
0
1
2
3
4
Tilt
(m
m/m
)
900
800
700
600
500
400
300
200
100
0
Sub
side
nce
(mm
)
During LW22
During LW23
During LW24B
During LW24A
Latest Survey (End of LW24A)
Predicted Profiles
270
272
274
276
278
280
282
284
286
288
290
Sur
face
Lev
el A
HD
(m
)
LW 22 LW 23A LW 24B LW 25
Dyke
T1
T6T11
T16
T21
T26T31
T36
T41 T46T51
T56
T61
T66T71 T76
T81
T86
Cracks
Pegs lost and replacedprior to start of LW24B
Tributary ofMyrtle Creek
ValleyClosure
Tributary ofMyrtle Creek
Upsidence nearbottom of valley
Change inLine Direction
Small bump in survey line
Survey line discontinuity
Thirlmere WayOverbridge
Systematiccompressivespike where
cracking and bumpobserved
in pavement
Fraser Stintersection
Changes inline direction
Nominal Survey Toleranceof ± 0.25 mm/m
over 20 m bay lengths
I:\Projects\Tahmoor\SurveyData\Thirlmere Way\Thirlmere Way Total (LW24A EOP).grf
(Roadworks)
Bumped peg(roadworks)
LW22
LW23A
LW24A
LW24B
Mine Subsidence Engineering Consultants Fig. MSEC335-24 Rev ?
1300 1350 1400 1450 1500 1550 1600 1650 1700 1750 1800Distance along Thirlmere Way from Survey Mark T1 (m)
-2.0
-1.5
-1.0
-0.5
0.0
0.5
1.0
1.5
2.0
Str
ain
(mm
/m)
LW 24B LW 25
-3
-2
-1
0
1
2
3
Tilt
(m
m/m
)
504540353025201510
50
-5-10-15
Sub
side
nce
(mm
)
During LW24A
Latest Survey
Predicted Profiles
260
265
270
275
280
285
290
Sur
face
Lev
el A
HD
(m
)
LW 24B LW 25
T6
4
T66
T68
T7
0 T72 T
74
T76
T78
T80 T8
2
T8
4 T8
6
Tahmoor Colliery - Incremental Subsidence Profilesalong Thirlmere Way during LW24A
Nominal Survey Toleranceof ± 0.25 mm/m
over 20 m bay lengths
I:\Projects\Tahmoor\SurveyData\Thirlmere Way\Thirlmere Way Inc (LW24A EOP).grf
LW22
LW23A
LW24A
LW24B
Mine Subsidence Engineering Consultants Fig. MSEC335-25 Rev ?
0 50 100 150 200 250 300 350 400Distance along Dam Line from Survey Mark Dam1 (m)
-2.0
-1.5
-1.0
-0.5
0.0
0.5
1.0
1.5
2.0
Str
ain
(mm
/m)
LW 24A
-4
-3
-2
-1
0
1
2
3
4
5
6
Tilt
(m
m/m
)
800
700
600
500
400
300
200
100
0
Sub
side
nce
(mm
)
During LW24A
Latest Survey
Predicted Profiles
250
255
260
265
270
275
280
Sur
face
Lev
el A
HD
(m
)
LW 24A
Dam
1
Dam
2
Dam
3
Da
m4
Da
m5
Da
m6
Dam
7
Da
m8
Dam
9
Da
m1
0
Da
m1
1
Dam
12
Da
m1
3
Dam
14
Dam
15
Dam
16
Da
m1
7
Da
m1
8
Dam
19
Tahmoor Colliery - Total Subsidence Profilesalong Inghams Dam Line
Nominal Survey Toleranceof ± 0.25 mm/m
over 20 m bay lengths
Note: It was predicted that up to 100mm of subsidence may occur in addition to predicted systematic subsidence between LW24A and 200 Panels
I:\Projects\Tahmoor\SurveyData\Inghams\Dam Line (LW24A EOP).grf
Monitoring line changesdirection at Peg Dam12
Monitoring line changesdirection at Peg Dam12
Small bump
Maximum compressive strainreduced from previous surveys
Elevated tensilestrain not repeatedin latest survey.
LW22
LW23A
LW24A
LW24B
Mine Subsidence Engineering Consultants Fig. MSEC335-26 Rev ?
0 50 100 150 200 250 300Distance along East-West Line from Survey Mark EW1 (m)
-2.0
-1.5
-1.0
-0.5
0.0
0.5
1.0
1.5
2.0
Str
ain
(mm
/m)
LW 24A
-1
0
1
2
3
4
5
6
7
Tilt
(m
m/m
)
700
600
500
400
300
200
100
0
Sub
side
nce
(mm
)
During LW24A
Latest Survey
Predicted Profiles
250
255
260
265
270
275
280
Sur
face
Lev
el A
HD
(m
)
LW 24A
EW
1
EW
2
EW
3
EW
4
EW
5
EW
6
EW
7
EW
8
EW
9
EW
10
EW
11
EW
12
Dam
14
Tahmoor Colliery - Total Subsidence Profilesalong Inghams East-West
Nominal Survey Toleranceof ± 0.25 mm/m
over 20 m bay lengths
Note: It was predicted that up to 100mm of subsidence may occur in addition to predicted systematic subsidence between LW24A and 200 Panels
I:\Projects\Tahmoor\SurveyData\Inghams\East-West Line (LW24A EOP).grf
LW22
LW23A
LW24A
LW24B
Mine Subsidence Engineering Consultants Fig. MSEC335-27 Rev ?
0 50 100 150 200 250 300 350 400 450Distance along High-Rise Freezer Line from Survey Mark NS7 (m)
-3.0
-2.5
-2.0
-1.5
-1.0
-0.5
0.0
0.5
1.0
1.5
2.0
Str
ain
(mm
/m)
LW 24A
-14-12-10
-8-6-4-202468
10
Tilt
(m
m/m
)
14001300120011001000
900800700600500400300200100
0
Sub
side
nce
(mm
)
During LW24A
Latest Survey
Predicted Profiles
250
255
260
265
270
275
280
Sur
face
Lev
el A
HD
(m
)
LW 24A
NS
7
HR
F1
HR
F2
HR
F3
HR
F4
HR
F5
HR
F6
HR
F7
HR
F8
HR
F9
HR
F1
0
HR
F1
1
HR
F1
2
HR
F1
3
HR
F14
HR
F15
HR
F16
HR
F1
7
HR
F18
Tahmoor Colliery - Total Subsidence Profilesalong Inghams High-Rise Freezer Line
Nominal Survey Toleranceof ± 0.25 mm/m
over 20 m bay lengths
Note: It was predicted that up to 100mm of subsidence may occur in addition to predicted systematic subsidence between LW24A and 200 Panels
I:\Projects\Tahmoor\SurveyData\Inghams\High-Rise Freezer Line (LW24A EOP).grf
Estimated subsidence forPegs HRF6 to HRF17
Upsidence in creekCreek does not extend
to urban area
Valley closure
LW22
LW23A
LW24A
LW24B
Mine Subsidence Engineering Consultants Fig. MSEC335-28 Rev ?
0 20 40 60 80 100 120 140 160 180 200Distance along North-South Line from Survey Mark EW7 (m)
-2.0
-1.5
-1.0
-0.5
0.0
0.5
1.0
1.5
2.0
Str
ain
(mm
/m)
-3
-2
-1
0
1
2
3
Tilt
(m
m/m
)
220200180160140120100
80604020
0
Sub
side
nce
(mm
)
During LW24A
Latest Survey
Predicted Profiles
255
260
265
270
275
280
285
Sur
face
Lev
el A
HD
(m
)
EW
7
NS
1
NS
2
NS
3
NS
4
NS
5
NS
6
NS
7
NS
8
NS
9
Tahmoor Colliery - Total Subsidence Profilesalong Inghams North-South
Nominal Survey Toleranceof ± 0.25 mm/m
over 20 m bay lengths
Note: It was predicted that up to 100mm of subsidence may occur in addition to predicted systematic subsidence between LW24A and 200 Panels
I:\Projects\Tahmoor\SurveyData\Inghams\North-South Line (LW24A EOP).grf
Compressive strains reducedfrom previous surveys.
LW22
LW23A
LW24A
LW24B
Mine Subsidence Engineering Consultants Fig. MSEC335-29 Rev ?
0 5 10 15 20 25 30 35 40 45 50 55 60 65Distance from PS1 (m)
-10
-8
-6
-4
-2
0
2
4
6
8
10
Diff
ere
ntia
l Hor
izon
tal M
ovem
ent
betw
een
adja
cent
peg
s (m
m)
-10
-8
-6
-4
-2
0
2
4
6
8
10
Diff
eren
tial V
ert
ical
Mov
emen
tbe
twe
en a
djac
ent p
egs
(mm
)
220200180160140120100
80604020
0
Sub
side
nce
(mm
)
During LW24A
Latest Survey
Predicted Profiles
255
260
265
270
275
280
285
Sur
face
Lev
el A
HD
(m
)
PS
1
PS
2
PS
3
PS
4
PS
5
PS
6
PS
7
PS
8
PS
9
PS
10
PS
11
PS
12
PS
13
PS
14
PS
15
Tahmoor Colliery - Total Subsidence Profilesalong Pipe Support Line (PS1 to PS15)
Note: It was predicted that up to 100mm of subsidence may occur in addition to predicted systematic subsidence between LW24A and 200 Panels
Change inline direction
I:\Projects\Tahmoor\SurveyData\Inghams\Pipe Supports (LW24A EOP).grf
Recommend that an extra 5 mm of subsidencebe added to results to account for later initial survey.
Trigger for Blue Level
Ammonia pipes redundantin this area.
Triggers for Blue Level
Trigger for Blue Level
Elevated closure notrepeated in latest survey.
LW22
LW23A
LW24A
LW24B
Mine Subsidence Engineering Consultants Fig. MSEC335-30 Rev ?
0 5 10 15 20 25 30 35 40Distance from PS16 (m)
-10
-8
-6
-4
-2
0
2
4
6
8
10
Diff
ere
ntia
l Hor
izon
tal M
ovem
ent
betw
een
adja
cent
peg
s (m
m)
-10
-8
-6
-4
-2
0
2
4
6
8
10
Diff
eren
tial V
ert
ical
Mov
emen
tbe
twe
en a
djac
ent p
egs
(mm
)
220200180160140120100
80604020
0
Sub
side
nce
(mm
)
During Lw24A
Latest Survey
Predicted Profiles
255
260
265
270
275
280
285
Sur
face
Lev
el A
HD
(m
)
PS
16
PS
17
PS
18
PS
19
PS
20
PS
21 12
PS
22
PS
23
Tahmoor Colliery - Total Subsidence Profilesalong Pipe Support Line (PS16 to PS23)
Note: It was predicted that up to 100mm of subsidence may occur in addition to predicted systematic subsidence between LW24A and 200 Panels
I:\Projects\Tahmoor\SurveyData\Inghams\Pipe Supports 16-23 (LW24A EOP).grf
Pipe Supports installed on 22nd February 2008.Approximately 28mm of subsidence had been
measured at Survey Mark 12 at this time.
Trigger for Blue Level
Triggers for Blue Level
Trigger for Blue Level
LW22
LW23A
LW24A
LW24B
Mine Subsidence Engineering Consultants Fig. MSEC335-31 Rev ?
0 50 100 150 200 250 300 350 400 450Distance from Survey Mark 1 (m)
-10
-8
-6
-4
-2
0
2
4
6
8
10
Diff
ere
ntia
l Hor
izon
tal M
ovem
ent
betw
een
adja
cent
peg
s (m
m)
-12-10
-8-6-4-202468
1012
Diff
eren
tial V
ert
ical
Mov
emen
tbe
twe
en a
djac
ent p
egs
(mm
)
220200180160140120100
80604020
0
Sub
side
nce
(mm
)
During LW24A
Latest Survey
Predicted Profiles
255
260
265
270
275
280
285
Sur
face
Lev
el A
HD
(m
)
12 3 4 5 6 7 89 10 11 12 13 14 15 16 17 18
19 20
21 22
23 24 25 26 27
28 29 30 31 32
33 34 35 36 37
38 3940
41 422
Tahmoor Colliery - Total Subsidence Profilesalong Inghams Plant Perimeter Line
Note: It was predicted that up to 100mm of subsidence may occur in addition to predicted systematic subsidence between LW24A and 200 Panels
Trigger for Blue Level
Recommend that an extra 5 mm of subsidencebe added to results to account for later initial survey.
I:\Projects\Tahmoor\SurveyData\Inghams\Plant (LW24A EOP).grf
No access to pegs dueto construction activity
Triggers for Blue Level
Trigger for Blue Level
High-Rise(north side)
High-Rise(south side)
Carton tunnel(north side)
Carton tunnel(south side)
Note: All elevated differential vertical movementsrelate to relatively long bay lengths
Mark 32 replaced
LW22
LW23A
LW24A
LW24B
Nail at Peg 13 bumped duringconstruction activity
Mine Subsidence Engineering Consultants Fig. MSEC335-32 Rev ?
0 100 200 300 400 500 600 700 800 900 1000Longwall Chainage (m)
0
10
20
30
40
50
Ups
ide
nce
and
Clo
sure
(m
m)
Upsidence
Closure
-10 0 10 20 30 40 50 60 70 80Distance along Mermaids Pool Line from Survey Mark M00 (m)
-10
-8
-6
-4
-2
0
2
4
6
8
10
Diff
eren
tial H
oriz
onta
l Mov
emen
tbe
twe
en a
djac
ent p
egs
(mm
)
30
20
10
0
-10
-20
-30
Sub
side
nce
(mm
)
During LW24A
Latest Survey
Nominal Survey Tolerance
0
10
20
30
40
50
Sur
face
Lev
el A
HD
(m
)
M00
M01
M02
M03
M04
M05
M06
M07
M08 M
09
M10 M11
M12
M13
Tahmoor Colliery - Total Subsidence Profilesalong Mermaids Pool Line across the Bargo River
I:\Projects\Tahmoor\SurveyData\Bargo River\Mermaid Pool\Mermaid (LW24A EOP).grf
LW24A
Mine Subsidence Engineering Consultants Fig. MSEC335-33 Rev ?
0 100 200 300 400 500 600 700 800 900 1000Longwall Chainage (m)
0
10
20
30
40
50
Ups
ide
nce
and
Clo
sure
(m
m)
Upsidence
Closure
-10 0 10 20 30 40 50Distance along X1 Line from Survey Mark X1-1 (m)
-10
-8
-6
-4
-2
0
2
4
6
8
10
Diff
eren
tial H
oriz
onta
l Mov
emen
tbe
twe
en a
djac
ent p
egs
(mm
)
30
20
10
0
-10
-20
-30
Sub
side
nce
(mm
)
During LW24A
Latest Survey
Nominal Survey Tolerance
45
46
47
48
49
50
51
52
53
54
55
Sur
face
Lev
el A
HD
(m
)
X1-
1
X1-
2
X1-
3
X1-
4
X1-
5
X1-
6 X1-
7
X1-
8
X1-
9
Tahmoor Colliery - Total Subsidence Profilesalong X1 Line across the Bargo River
X1 Line is not connected to datum.Subsidence is relative only.
I:\Projects\Tahmoor\SurveyData\Bargo River\Rockbars\X1 Line (LW24A EOP).grf
LW24A
Mine Subsidence Engineering Consultants Fig. MSEC335-34 Rev ?
0 100 200 300 400 500 600 700 800 900 1000Longwall Chainage (m)
0
10
20
30
40
50
Ups
ide
nce
and
Clo
sure
(m
m)
Upsidence
Closure
-10 0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160 170Distance along X2 Line from Survey Mark X2-L (m)
-10-8-6-4-202468
1012
Diff
eren
tial H
oriz
onta
l Mov
emen
tbe
twe
en a
djac
ent p
egs
(mm
)
30
20
10
0
-10
-20
-30
Sub
side
nce
(mm
)
During LW24A
Latest Survey
180
190
200
210
220
230
240
250
260
270
Sur
face
Lev
el A
HD
(m
) X2-
L
X2-
1
X2-
2
X2-
3X
2-4
X2-
5X
2-6
X2-
7 X2-
8
X2-
R
Tahmoor Colliery - Total Subsidence Profilesalong X2 Line across the Bargo River
Level connection betweenPeg X2-L and X2-6. Surveytolerance of level connectioninto gorge of ± 10 mm.
X2-L not connected todatum. Subsidence isrelative only.
Relative survey tolerance of levels inbase of gorge ± 3 mm.
I:\Projects\Tahmoor\SurveyData\Bargo River\Rockbars\X2 Line (LW24A EOP).grf
LW24A
Mine Subsidence Engineering Consultants Fig. MSEC335-35 Rev ?
0 100 200 300 400 500 600 700 800 900 1000Longwall Chainage (m)
0
10
20
30
40
50
Ups
ide
nce
and
Clo
sure
(m
m)
Upsidence
Closure
-10 0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160 170Distance along X3 Line from Survey Mark X3-L (m)
-10
-8
-6
-4
-2
0
2
4
6
8
10
Diff
eren
tial H
oriz
onta
l Mov
emen
t b
etw
een
adja
cent
peg
s (m
m)
30
20
10
0
-10
-20
-30
Sub
side
nce
(mm
)
During LW24A
Latest Survey
170
180
190
200
210
220
230
240
250
260
270
Sur
face
Lev
el A
HD
(m
)
X3-
L
X3-
1
X3-
2 X3-
3
X3-
R
Tahmoor Colliery - Total Subsidence Profilesalong X3 Line across the Bargo River
Level connection betweenPeg X3a-L and X3-2. Surveytolerance of level connectioninto gorge of ± 10 mm.
Peg X3a-L destroyed and replaced on 15 Feb 08.Subsidence returned to zero for replaced X3a-L.Increased subsidence for X3a pegs in gorgemeasured since Peg X3a-L was replaced.Peg X3a-L destroyed again on 17-Apr 08.
Relative survey tolerance of levels inbase of gorge ± 3 mm.
I:\Projects\Tahmoor\SurveyData\Bargo River\Rockbars\X3 Line (LW24A EOP).grf
LW24A
Mine Subsidence Engineering Consultants Fig. MSEC335-36 Rev ?
0 100 200 300 400 500 600 700 800 900 1000Longwall Chainage (m)
0
10
20
30
40
50
Ups
ide
nce
and
Clo
sure
(m
m)
Upsidence
Closure
-10 0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160 170 180Distance along X3a Line from Survey Mark X3a-L (m)
-10
-5
0
5
10
15
20
Diff
eren
tial H
oriz
onta
l Mov
emen
tbe
ttwee
n ad
jace
nt p
egs
(mm
)
30
20
10
0
-10
-20
-30
Sub
side
nce
(mm
)
During LW24A
Latest Survey
160
170
180
190
200
210
220
230
240
250
260
270
Sur
face
Lev
el A
HD
(m
) X3a
-L
X3a
-1
X3a
-2
X3a
-3X
3a-4
X3a
-5
X3a
-6
X3a
-R
Tahmoor Colliery - Total Subsidence Profilesalong X3a Line across the Bargo River
Level connection betweenPeg X3a-L and X3a-6. Surveytolerance of level connectioninto gorge of ± 10 mm.
Peg X3a-L destroyed and replaced on 15 Feb 08.Subsidence returned to zero for replaced X3a-L.Increased subsidence for X3a pegs in gorgemeasured since Peg X3a-L was replaced.Peg X3a-L destroyed again on 17-Apr 08.Subsidence for this survey normalised basedon subsidence at nearby Peg 25-1.
Relative survey tolerance of levels inbase of gorge ± 3 mm.
Peg X3a5 destroyed and replacedon 17-Apr-08.Subsidence normalised to matchsubsidence of adjacent pegs.
I:\Projects\Tahmoor\SurveyData\Bargo River\Rockbars\X3a Line (LW24A EOP).grf
LW24A
Mine Subsidence Engineering Consultants Fig. MSEC335-37 Rev ?
0 100 200 300 400 500 600 700 800 900 1000Longwall Chainage (m)
0
10
20
30
40
50
Ups
ide
nce
and
Clo
sure
(m
m)
Upsidence
Closure
-10 0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160 170Distance along X4 Line from Survey Mark X4-0 (m)
-10
-5
0
5
10
15
20
25
30
Diff
eren
tial H
oriz
onta
l Mov
emen
tbe
twe
en a
djac
ent p
egs
(mm
)
30
20
10
0
-10
-20
-30
Sub
side
nce
(mm
)
During LW24A
Latest Survey
160
170
180
190
200
210
220
230
240
250
260
Sur
face
Lev
el A
HD
(m
)
X4-
L
X4-
0
X4-
1
X4-
2
X4-
3X
4-4
X4-
5X
4-6
X4-
7
X4-
R
Tahmoor Colliery - Total Subsidence Profilesalong X4 Line across the Bargo River
Level connection betweenPeg X4-L and X4-5. Surveytolerance of level connectioninto gorge of ± 10 mm.
Relative survey tolerance of levels inbase of gorge ± 3 mm.
I:\Projects\Tahmoor\SurveyData\Bargo River\Rockbars\X4 Line (LW24A EOP).grf
LW24A
Mine Subsidence Engineering Consultants Fig. MSEC335-38 Rev ?
0 100 200 300 400 500 600 700 800 900 1000Longwall Chainage (m)
0
10
20
30
40
50
Ups
ide
nce
and
Clo
sure
(m
m)
Upsidence
Closure
-10 0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160 170Distance along X5a Line from Survey Mark X5-L (m)
-10
-8
-6
-4
-2
0
2
4
6
8
10
Diff
eren
tial H
oriz
onta
l Mov
emen
tbe
twe
en a
djac
ent p
egs
(mm
)
30
20
10
0
-10
-20
-30
Sub
side
nce
(mm
)
During LW24A
Latest Survey
160
170
180
190
200
210
220
230
240
250
260
Sur
face
Lev
el A
HD
(m
) X5-
L
X5a
-1
X5a
-2X
5a-3
X5a
-4
X5a
-5X
5a-6
X5a
-7
X5-
R
Tahmoor Colliery - Total Subsidence Profilesalong X5a Line across the Bargo River
Level connection betweenPeg X5-L and X5a-5. Surveytolerance of level connectioninto gorge of ± 10 mm.
Relative survey tolerance of levels inbase of gorge ± 3 mm.
I:\Projects\Tahmoor\SurveyData\Bargo River\Rockbars\X5a Line (LW24A EOP).grf
LW24A
Mine Subsidence Engineering Consultants Fig. MSEC335-39 Rev ?
0 100 200 300 400 500 600 700 800 900 1000Longwall Chainage (m)
0
10
20
30
40
50
Ups
ide
nce
and
Clo
sure
(m
m)
Upsidence
Closure
-10 0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160 170Distance along X5b Line from Survey Mark X5-L (m)
-10
-8
-6
-4
-2
0
2
4
6
8
10
Diff
eren
tial H
oriz
onta
l Mov
emen
tbe
twe
en a
djac
ent p
egs
(mm
)
30
20
10
0
-10
-20
-30
Sub
side
nce
(mm
)
During LW24A
Latest Survey
160
170
180
190
200
210
220
230
240
250
260
Sur
face
Lev
el A
HD
(m
) X5-
L
X5b
-1
X5b
-2X
5b-3
X5b
-4
X5b
-5
X5b
-6X
5b-7 X5b
-8
X5-
R
Tahmoor Colliery - Total Subsidence Profilesalong X5b Line across the Bargo River
Level connection betweenPeg X5-L and X5b-7. Surveytolerance of level connectioninto gorge of ± 10 mm.
Relative survey tolerance of levels inbase of gorge ± 3 mm.
I:\Projects\Tahmoor\SurveyData\Bargo River\Rockbars\X5b Line (LW24A EOP).grf
LW24A
Mine Subsidence Engineering Consultants Fig. MSEC335-40 Rev ?
0 100 200 300 400 500 600 700 800 900 1000Longwall Chainage (m)
0
10
20
30
40
50
Ups
ide
nce
and
Clo
sure
(m
m)
Upsidence
Closure
-10 0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160 170 180 190 200 210Distance along X5c Line from Survey Mark X5-L (m)
-10
-8
-6
-4
-2
0
2
4
6
8
10
Diff
eren
tial h
oriz
onta
l Mov
emen
tbe
twe
en a
djac
ent p
egs
(mm
)
30
20
10
0
-10
-20
-30
Sub
side
nce
(mm
)
During LW24A
Latest Survey
150
160
170
180
190
200
210
220
230
240
250
260
Sur
face
Lev
el A
HD
(m
)
X5-
L
X5c
-1
X5c
-2X
5c-3
X5c
-4X
5c-5
X5c
-6X
5c-7
X5c
-8
X5-
R
Tahmoor Colliery - Total Subsidence Profilesalong X5c Line across the Bargo River
Level connection betweenPeg X5-L and X5c-7. Surveytolerance of level connectioninto gorge of ± 10 mm.
Tree has grown and restrictedline of sight from X5-L to X5c-7.Eccentric setup used for levelconnection for March survey.Level to X5c-7 now connectedby X5a and X5b base pegs.
Relative survey tolerance of levels inbase of gorge ± 3 mm.
I:\Projects\Tahmoor\SurveyData\Bargo River\Rockbars\X5c Line (LW24A EOP).grf
LW24A
Mine Subsidence Engineering Consultants Fig. MSEC355-41 Rev ?
0 100 200 300 400 500 600 700 800 900 1000Longwall Chainage (m)
0
10
20
30
40
50
Ups
ide
nce
and
Clo
sure
(m
m)
Upsidence
Closure
-20 0 20 40 60 80 100 120 140 160 180 200 220 240 260Distance along X6 Line from Survey Mark X6-L (m)
-10
-8
-6
-4
-2
0
2
4
6
8
10
Diff
eren
tial H
oriz
onta
l Mov
emen
tbe
twe
en a
djac
ent p
egs
(mm
)
30
20
10
0
-10
-20
-30
Sub
side
nce
(mm
)
During LW24A
Latest Survey
140
160
180
200
220
240
260
280
Sur
face
Lev
el A
HD
(m
) X6-
L
X6-
1
X6-
2X
6-3
X6-
4X
6-5
X6-
6X
6-7
X6-
8
X6-
R
Tahmoor Colliery - Total Subsidence Profilesalong X6 Line across the Bargo River
Level connection betweenPeg X6-L and X6-6. Surveytolerance of level connectioninto gorge of ± 10 mm.
X6-L not connected todatum. Subsidence isrelative only.
Survey error, notrepeated in currentsurvey.
Relative survey tolerance of levels inbase of gorge ± 3 mm.
I:\Projects\Tahmoor\SurveyData\Bargo River\Rockbars\X6 Line (LW24A EOP).grf
LW24A
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