BAR RevA Resubmission - 24 Dec 2010

8/7/2019 BAR RevA Resubmission - 24 Dec 2010

1/402

07257/I2/G/R014A

Contract No. DC/2007/12Design and Construction of Tsuen Wan Drainage Tunnel

Blasting Assessment Report for Intake I-2

December 2010


2/402


3/402

Contract No. DC/2007/12Design and Construction of Tsuen Wan Drainage TunnelBlasting Assessment Report for Intake I-2 (Rev A)

EXECUTIVE SUMMARY

The proposed works covered by this blast assessment include all drill and blast operations in

connection with the hard rock excavation of the lower sections of the Vortex Drop Shaft and the

Upper Man Access Shafts, the Upper and Lower connecting Man Access Adits, the Lower Man

Access Shaft, De-aeration Chamber and Main Adit at the Intake I-2, Lo Wai, Tsuen Wan.

Various types of sensitive receivers have been identified close to the proposed blasting areas with

some having a higher order of ranking than others. In particular there are slopes and the Ship

Temple () within the locality and identified as being in close proximity to the blastareas at the Intake I-2 location.

For any geotechnical features located within the influence of the blasting areas, stability analysishas been carried out to determine the safe vibration levels for such features. It has been

determined that any sensitive receivers subjected to a PPV less than 5mm/s will not require

detailed assessment unless preconstruction condition survey suggests the feature may be

unusually sensitive to blasting vibrations.


4/402

CONTENTS

1.0 INTRODUCTION ................................................................................................................................... 1

1.1 Background ........................................................................................................................................ 1

1.2 Government Blasting Requirements .................................................................................................. 1

1.3 Scope of Report ................................................................................................................................. 2

1.4 Structure of Report ............................................................................................................................ 3

1.5 Report Limitation ................................................................................................................................ 3

1.6 Reference to Other Relevant Reports ............................................................................................... 3

2.0 PROPOSED BLASTING LOCATIONS ................................................................................................. 4

2.1 General .............................................................................................................................................. 4

2.2 INTAKE I-2 Area ................................................................................................................................ 4

3.0 TOPOGRAPHIC, GEOLOGIC AND HYDROGEOLOGIC STUDY ....................................................... 5

3.1 General .............................................................................................................................................. 5

3.2 Geology .............................................................................................................................................. 5

3.3 Published Geology ............................................................................................................................. 5

3.4 Previous Ground Investigations ......................................................................................................... 6

3.5 Groundwater ...................................................................................................................................... 6

3 6 Ph i l Sit C t i t 7


5/402

6.9 Natural Terrain Hillside and Boulders .............................................................................................. 20

6.10 Existing Buildings and Structures .................................................................................................... 20

6.11 Historical Buildings and Monuments ............................................................................................... 22

6.12 WSD Facilities ................................................................................................................................. 22

6.13 Utility Companies ............................................................................................................................. 23

6.14 Other Facilities ................................................................................................................................. 23

6.15 Controlling Sensitive Receivers ....................................................................................................... 24

7.0 CONSTRUCTION REQUIREMENTS .................................................................................................. 25

7.1 Proposed Blasting Areas ................................................................................................................. 25

7.2 Estimates and Quantities of Explosives Required ........................................................................... 25

7.3 Explosives Delivery .......................................................................................................................... 25

7.4 Tunnel Blasting operations .............................................................................................................. 25

7.4.1 Shafts at Intake I-2 ................................................................................................................... 267.4.2 As Constructed Air Vent Shaft ................................................................................................. 27

7.4.3 Pre-Constructed Main Tunnel .................................................................................................. 27

7.4.4 Tunnel Blasting Procedure ...................................................................................................... 27

8.0 BLASTING CONTAINMENT AND CONTROL MEASURES ............................................................. 30

8.1 Blast Restrictions and Control Levels .............................................................................................. 30


6/402

TABLES

Table 3.5: INTAKE I-2 WATERTABLE 7

Table 4.0: REFERENCE TO AS-CONSTRUCTED STRUCTURES 9

Table 5.2: TYPICAL CHARGE WEIGHT PER DELAY AGAINST DISTANCE ANDPPVC

11

Table 5.3a: CORRESPONDENCE WITH UTILITY COMPANIES 12

Table 5.3b: VIBRATION LIMITS AS DETERMINED BY UTILITY COMPANIES INHONG KONG

12

Table 5.4a: STRUCTURAL BEHAVIOUR SUBJECT TO AIRBORNE VIBRATION 14

Table 5.4b: TYPICAL CHARGE WEIGHT PER DELAY VERSUS DISTANCE ANDDBL

15

Table 6.5: PARTIAL FACTORS APPLIED TO LOADING AND MATERIALPARAMETERS

19

Table 6.8: SUMMARY TABLE OF AFFECTED MAN-MADE FEATURES NEARINTAKE I-2

20

Table 6.10: SUMMARY TABLE OF AFFECTED BUILDINGS AND STRUCTURES 22

Table 6.12: SUMMARY TABLE OF AFFECTED MAJOR WSD FACILITIES 23

Table 6.13: SUMMARY TABLE OF AFFECTED MAJOR UTILITIES 23

Table 6.14: SUMMARY TABLE OF OTHER AFFECTED FACILITIES 24

T bl 8 1 BLAST VIBRATION CONTROL PROCEDURE 30


7/402

APPENDICES

APPENDIX A OVERALL LAYOUT OF THE INTAKE I-2

APPENDIX B GEOLOGICAL SECTION OF INTAKE I-2

APPENDIX C REFERENCE DRAWINGS FOR INTAKE I-2

APPENDIX D ROCKHEAD AND GROUNDWATER CONTOURS PLAN

APPENDIX E INVENTORY OF EXISTING BUILDINGS

APPENDIX F DRAWINGS OF EXISTING UTILITIESAPPENDIX G TYPICAL BLAST PATTERNS

APPENDIX H ASSESSMENT OF AFFECTED MAN-MADE SLOPES AND RETAININGWALLS

APPENDIX I ASSESSMENT OF EXISTING FACILITIES

APPENDIX J EXPLOSIVE QUANTITIES AND DELIVERY SCHEDULE

APPENDIX K INSTRUMENTATION LAYOUT PLANAPPENDIX L PROPOSED PROTECTIVE MEASURES

APPENDIX M BOREHOLE LOCATION PLAN AND GROUNDWATER MONITORINGRECORDS

APPENDIX N REPORT FOR SOUND INSULATION MEASUREMENT TEST

APPENDIX O DOCUMENTARY RECORD OF PUBLIC CONSULTATION


8/402


1.0 INTRODUCTION

1.1 BACKGROUND

The Tsuen Wan Drainage Tunnel (TWDT) has been commissioned to improvethe flood protection level in the Tsuen Wan and Kwai Chung area by constructinga drainage tunnel system to intercept flow from upland catchments. The tunnelsystem will comprise:

an Intake Structure at the junction of Wo Yi Hop Road and Shing Mun Road(I-1);

an Intake Structure at Lo Wai (I-2);

an Intake Structure at Tso Kung Tam, about 350m off the southern side ofRoute Twisk (I-3);

an Outfall Structure at Yau Kom Tau underneath Castle Peak Road (O-1);

a 5.1km long, 6.5m diameter Main Tunnel with associated adit tunnelsconnected to the various intake structures.

Currently the excavation of the Intake at I-2 is being undertaken usingmechanical means which gives the geology of the area, slightly decomposedtuff, rates of excavation are consequently slow.

The current view of the contractor is that to maintain the constructionprogramme of Intake I-2 excavation will have to be completed using blastingmethods. However, given the locality of the site and the proximity of variouslocal structures, the purpose of this report is to assess the undertaking of


9/402


Report (BAR) are contained in Geotechnical Engineering Office (GEO) Circular

No. 27.These blasting requirements are also noted and defined in PNAP 178 for thoseprivate projects that are under taken through the Buildings Department (BD)Ordinance.

1.3 SCOPE OF REPORT

This BAR refers to the portion of Works referred to in Section 1.1 above.

This BAR is prepared in order to determine the sensitive receivers within thevicinity of the pre-determined blast areas, the likely restrictions that they willimpose on blasting and appropriate control measures that should beimplemented in order to ensure blasting is carried out safely. This will then allowan evaluation of the feasibility of blasting.

An initial review of the various blast site constraints indicates that a maximumexplosive charge-weight of 0.2 kg / 0.33 kg per delay determined through designof blast pattern will allow normal excavation progress of the Intake I-2 Shafts and

Man Access Adits, and 0.4kg per delay for the De-aeration Chamber and MainAdit. Based on this maximum charge-weight and using the standard MinesDivision blast prediction formula, it has been calculated that the level of vibrationdue to blasting would have an attenuation of less than 5mm/s at a radial distanceof 30m from 0.33kg per delay blasting point or 34m from 0.4kg per delay blastingpoint. These values correspond with the vibration limit typically applied to historicbuildings, buildings in poor condition or of unknown design quality. It hastherefore been determined that any sensitive receivers subjected to less than


10/402


A 4m ID Man Access Shaft (Lower),

A 3.5m ID Man Access Adit (Upper), and

The commencement of blasting for 14m, from a depth of approximately 25mbelow ground level, within a single 4m ID Man Access Shaft (Upper) whichhas a total depth of approximately 39m.

The overall layout of Intake I-2 is shown in Drawing MCSJV/TW/I-2/2020102located in Appendix A.

The shafts and tunnels will be constructed within rock and it is anticipated thatthe excavation will be by drill and blast methods. This blasting assessmenttherefore has been prepared in accordance with GEO Circular No.27.

1.4 STRUCTURE OF REPORT

The Blasting Assessment Report (BAR) covers a small section of the Works atIntake I-2 that constitutes the tunnel alignment between Intake I-2 and the maintunnel alignment making reference to the various individual sensitive receivers

and local blasting issues within the area.This report contains general background information relevant to the wholealignment detailing the topographical, geological and hydrological setting.It alsodescribes the general blasting approach related to each blast area outlining theassociated blasting constraints for each of the blast areas as well as therequirements for supervision and inspection that will be adopted for the whole ofthe alignment blasting works.

1.5 REPORT LIMITATION


11/402


2.0 PROPOSED BLASTING LOCATIONS

2.1 GENERAL

The proposed works covered by this blast assessment include all drill and blastoperations in connection with the excavation in hard rock in the followingsections of the Works:

A single 5m ID and 5.84m OD Vortex Drop Shaft which has a total depth ofapproximately 30m,

A De-aeration Chamber of approximately 21m long by 9m wide by 13m high, A 3.5m ID and 4.24m OD Man Access Adit (Lower),

A 4m ID and 4.74m OD Man Access Shaft (Lower),

A 4.5m ID and 5.6m OD Main Adit,

A 3.5m ID and 4.24m OD Man Access Adit (Upper), and

A single 4m ID and 4.74m OD Man Access Shaft (Upper) which has a total

depth of approximately 39m.

A layout plan for each of these areas is shown in the accompanying drawing:MCSJV/TW/I-2/2020102 inclusive and geological sections of these areas areshown in MCSJV/TW/I-2/2020108 respectively. These drawings are located inAppendices A and B respectively.

2.2 INTAKE I-2 AREA

The proposed Main Tunnel extends from its eastern end in the Sheung Kwai


12/402


3.0 TOPOGRAPHIC, GEOLOGIC AND HYDROGEOLOGIC STUDY

3.1 GENERAL

The proposed Intake I-2 is located in a major stream course adjacent to Lo WaiRoad bridge crossing. There is extensive surface development at Lo Waiincluding the Yuen Yuen Home for The Aged to the northwest of the intake,Yuen Yuen Institute to the north and Hilltop Country Club to the northeast. Thetopography in section along the alignment is shown in geological sections underdrawing MCSJV/TW/I-2/2020108 and the inferred rockhead contour is shown in

drawing MCSJV/TW/I-2/2020109. These drawings are located in Appendices Band D respectively. The borehole information is included in Appendix M.

3.2 GEOLOGY

In accordance with the information presented in the Geotechnical BaselineReport (GBR), Intake I-2 will be excavated entirely within volcanic coarse ash tuffof the Yim Tin Tsai Formation. It is described as dense greenish grey to darkgrey, very fine to fine-to-medium grained crystalline rock.

The coarse ash tuff is generally strong to very strong (79 MPa to 374 MPa) andis highly abrasive. The rock joints are generally medium to widely-spaced andare predominantly sub-vertical. Low angle sheeting joints also occur, particularlytowards the ground surface. Joints and micro-fissures have complex jointspacing varying from very close to widely and occasionally very widely spaced.The joints are rough/planar to smooth/planar, with Fe/Mn staining or Ch/Qu/Cafill. There are typically 4 sets of joints (3 subvertical and 1 horizontal); some ENEbasalt dykes are likely.


13/402


3.4 PREVIOUS GROUND INVESTIGATIONS

GIU Report No. 42632

This report comprises a Final Fieldwork Report for the ground investigation (GI)works of Feature No. 7SW-C/R86. The GI works consist of 3 drillholes (CH1 toCH3), 5 coreholes (CH4 to CH8) and a trial trench (TT1) which are located atapproximately 80m to 90m from the proposed Intake I-2. The drillholes revealedthat the underlying geology comprises a thin layer of Fill overlying Alluvium andDecomposed Tuff. Bedrock was encountered at about 4m below ground. The

groundwater monitoring records at CH3 indicated that the groundwater level is atabout 3.7m below ground (+87.40mPD).


This report comprises a Final Fieldwork Report for the GI works of Feature No.7SW-A/R39. The GI works consist of 1 drillhole (BH1) and 2 trial pits (TP1 andTP2) which are located at approximately 60m from the proposed Intake I-2.Drillhole No. BH1 revealed that the underlying geology comprises a layer of Filloverlying Slightly Decomposed Tuff (SDT). Bedrock was encountered at about2.6m below ground. The groundwater monitoring records at BH1 indicated thatdry condition is occurred at about 3.5m below ground (+109.02mPD).


This report comprises a Final Fieldwork Report for the GI works of Feature No.7SW-A/R39. The GI works consist of 4 coreholes (CH1 to CH4) which arelocated at approximately 60m from the proposed Intake I-2. The coreholesrevealed that the underlying geology comprises a layer of Fill overlying Slightly


14/402


monitoring records show significant variations in the highest monitored

groundwater levels (HMGWL) which vary between regolith layer and bedrockthroughout the tunnel alignment.

The GBR states the baseline conditions for groundwater levels are as follows:Except where stated otherwise, the watertable lies within 1 m of rockhead in thewet season, rising into the regolith to within 1 m of the ground surface duringrainstorms. Perennial artesian groundwater (1 m higher than the ground coverand higher during rainstorms) occurs across the Lo Wai valley adjacent to IntakeI-2.

From the recent groundwater monitoring data, the recorded highest and lowestgroundwater levels for relevant areas are presented in the table below.

Borehole No. Monitoring Period HighestGroundwater Level

(mPD)

Lowest GroundwaterLevel (mPD)

I2/BH511 Aug 2009

14 Aug 2010 105.16 103.71

I2/BH10A30 Sept 2008

16 Aug 2010102.41 99.86

I2/BH11A30 Sept 2008

18 Aug 2010105.71 98.10


15/402


Various types of sensitive receivers have been identified close to the proposed

blasting areas with some having a higher order of ranking than others. Inparticular there are slopes and the Ship Temple () within the localityand identified as being in close proximity to the blast areas at the Intake I-2location.

However, as part of the Pre-condition and Structural Survey, the nearby buildingstructures have been identified as being either in close proximity to the alignmentor one of the designated blast areas. Reference is made to drawingMCSJV/TW/I-2/2020114 which highlights these structures locality and also theinventory of existing buildings. This information is located in Appendix E forreference.

3.7 EXISTING UTILITIES

In addition to the existing building structures, numerous existing utilities arelocated in the vicinity of the designated blasting area and the utilities undertakersinclude the following:

Drainage Service Department PCCW Ltd.

Water Supplies Department

Hong Kong & China Gas Ltd (Towngas)

CLP Power Hog Kong Ltd.

The location of the existing utilities in the vicinity of the different blast areas are


16/402


4.0 PROPOSED LAYOUTS OF THE SHAFTS AND ADIT CONNECTIONS

It is from the Upper Man Access Shaft and Vortex Drop Shaft that the drill andblast excavation of the Intake I-2 will start and the shafts will be the only meansof access and egress to men, material and plant until the connecting aditsintersect the De-aeration Chamber.

The shaft area is already established as other surface works have alreadycommenced and there have been some retaining measures undertaken tosupport the adjacent slopes and surrounding area.

Details of the as-constructed structures are included in Appendix C as listed inthe table below.

As-constructed Structures Reference Drawings

Noise Enclosure above Upper ManAccess Shaft

MCSJV/TW/I-2/2012090 to 2012094,2012101 and 2012209 to 2012212

Noise enclosure above Vortex DropShaft

MCSJV/TW/I-2/2012095 to 2012098and 2012100

Air Vent Shaft MCSJV/PW/I-2/2030025

Approach Channel DC/2001/12/SK/072, 0471 and 0459,MCL/4111CD/S/220 and 223,MCSJV/SK/I-2/2104067 and 2104068

Solider-pile Wall MCL/4111CD/G/209,DC2007/12/SK/0056, 0068, 0149, 0221,


17/402


5.0 BLASTING MECHANISM AND POSSIBLE DETRIMENTAL EFFECTS

5.1 GENERAL

The maximum charge weight that will be used during the Intake I-2 blastingworks was calculated based on the limited PPV of the sensitive receivers in thevicinity of the site and has been found to not exceed 0.2 kg / 0.33 kg per delayfor the Shafts and 0.4kg per delay for the Chamber and Main Adit. Whereverused these will enable a pull, that is blasted advance, of around 0.8m to 1.0m tobe gained for full face blasting. This rate of advance is deemed optimal when

consideration is made of the practicable constraints such as the excavation cycletimes taken for the development of the shaft, adit and de-aeration chamber. Themaximum charge weight table for Intake I-2 has been presented in drawingMCSJV/TW/I-2/2020116 in Appendix G. The results have been summarized andshown in drawing MCSJV/TW/I-2/2020117. And the typical blast pattern designsfor the shaft, adit and de-aeration chamber are also shown in Appendix G.

5.2 GROUND VIBRATION

It is observed that ground vibrations induced by blast stress wave have a peakvelocity that is related to the instantaneous charge weight and the distance fromthe blast source. A preliminary assessment of the ground vibrations likely toresult from blasting can be made using the formula as shown derived by theUnited States Bureau of Mines:

PPV = K (R/ W)-B

This formula has been adopted by the Mines Division of the Hong KongGovernment, which has monitored blasting vibrations in Hong Kong since 1965.


18/402


Allowable Charge Weight (kg/delay)

RadialDistancefromB

last(m)

Distance6.00 5.00 4.00 3.00 2.00 1.00 0.50 0.25 0.10

Predicted Peak Particle Velocity (PPV) (mm/sec)

120 5.6 5.0 4.4 3.7 2.9 1.9 1.2 0.8 0.5

100 7.0 6.2 5.4 4.6 3.6 2.3 1.5 1.0 0.6

90 7.9 7.1 6.2 5.2 4.1 2.7 1.7 1.1 0.7

80 9.2 8.2 7.2 6.0 4.7 3.1 2.0 1.3 0.8

70 10.8 9.6 8.4 7.1 5.5 3.6 2.4 1.6 0.965 11.8 10.6 9.2 7.7 6.0 4.0 2.6 1.7 1.0

60 13.0 11.6 10.2 8.5 6.7 4.4 2.9 1.9 1.1

55 14.5 12.9 11.3 9.5 7.4 4.8 3.2 2.1 1.2

50 16.2 14.5 12.7 10.6 8.3 5.4 3.6 2.3 1.3

45 18.5 16.5 14.4 12.1 9.5 6.2 4.1 2.7 1.5

40 21.3 19.1 16.7 14.0 10.9 7.2 4.7 3.1 1.8

35 25.1 22.5 19.6 16.5 12.8 8.4 5.5 3.6 2.1

30 30.3 27.1 23.7 19.9 15.5 10.2 6.7 4.4 2.525 37.9 33.9 29.6 24.8 19.4 12.7 8.3 5.4 3.1

20 49.7 44.5 38.8 32.6 25.4 16.7 10.9 7.2 4.1

15 70.6 63.2 55.1 46.2 36.1 23.7 15.5 10.2 5.8

10 115.8 103.6 90.4 75.8 59.2 38.8 25.4 16.7 9.5

5 269.7 241.3 210.6 176.7 138.0 90.4 59.2 38.8 22.2

Table 5.2 : Typical Charge weight per delay against Distance and PPVc


19/402


Utility Request on Letter Ref. Reply on Letter Ref.

WSD

21 Jul 201007257/

339555

3 Aug 2010(3) in WSD/NTW486/70/125/2006 TJ(7)

Towngas 23 Jul 2010 UNE2010/03636/N

CLP - -*

DSD 6 Sept 2010(176918) in MS

9/DC2007/12/0/0PCCW 23 Jul 2010 OPS/NT/WKC/RW-605

Wharf T&T Ltd 30 Jul 2010 WTT/NT10//0680/KSW

HighwaysDepartment

- -*

Table 5.3a:Correspondence with Utility Companies

Note: * Allowable PPV based on ER Clause 4.4.4 (5). Extract of ER has been included inAppendix F.

Utility InstallationPPV(mm/sec)

Max Amplitude

WSD Water retaining structures / WaterTunnels

13 0.1mm

Water Mains / Other structures and pipes 25 0.2mm


20/402


assessment shall be prepared based on the acceptable vibration levels agreed

by the utilities operators.The Utilities affected by the project are located in Appendix F for reference.

5.4 AIR BLAST AND NOISE CRITERIA

Air-blasts and construction noise are the common description of air pressurewaves generated by explosive detonation and construction machinery.

The pressure waves can be described with time histories where amplitude is air

pressure. Construction noise is the audible, high frequency portion of thepressure wave. The lower frequency portion is the air-blast, which is not audible,but excites structures and buildings to produce noise through rattling windowsetc.

The pressure wave generated by an explosion also propagates through air,forming an airborne vibration in the form of concussion or air overpressure.Noise is the audible result of this pressure wave, with frequencies from 20 to20,000 Hz, while air blast lies in the inaudible range below 20 Hz.

Measurement of sound pressure is made in decibels (dB). The decibel scale islogarithmic and allows the compression of zero to one kPa into a range of about150 dB. An increase of 6 dB represents a doubling of the sound pressure and anincrease of about 3 dB occurs as a result of the sound doubling (for example 2machines instead of one). A noise level of about 100 dB is very loud, 140 dBpainfully loud and 180 dB will lead to irreversible hearing loss.

The human perception of sound, which is more sensitive to some frequenciesthan others, has led to the development of weighting scales to simulate the


21/402


SymptomsPeak Overpressure

kPa dB

Rattle of loose window sash against window frame 0.2 140

Failure of poorly mounted window pane 0.7 150

Damage to strongly mounted window pane 7 170

Cracking plaster > 7 > 170

Table 5.4a: Structural behaviour subject to airborne vibration.

Airblast is usually controlled by wind speed and direction, humidity, temperature,topography, type and amount of explosives used, depth of explosives buried,geology etc.

The US Bureau of Mines recommends the following safe levels for airblast (forevents exceeding 2 seconds duration):

135 dB when using a 0.1 Hz high pass linear measurement method, or

133 dB when using a 2 Hz high pass response, and

129 dB for a frequency range of 6 to 200 Hz

Noise from blasting is exempt from consideration under a Construction Noise


22/402


blasting operations and typical blasting times. The schematic temporary traffic

arrangement is enclosed in Appendix J for reference.The Mines Division target for air overpressure will be complied with and will bedetermined in dBL. At the time of writing this report, 120dBL is the Mines Divisiontarget for allowable air-overpressure.

Usually Mines Division applies this target for air blast for sites in Hong Kongalthough there is some flexibility on the limit dependent on the number ofcomplaints received.

The following analysis for the allowable air overpressure is based upon siteformation derived constant from various surface projects in Hong Kong. Theequation outlined below is one used by Mines Division to check the allowable airoverpressure close to the blast.

Air overpressure (dBL) = 170 24log10 [ D/W0.333

]

Table 5.4b presents the typical range of charge weights and predicted vibrationlevels using the Mines Division vibration constants.

This analysis is really only applicable to surface blasting although it can be usedtentatively when blasting is carried out in tunnel areas close to the portal or shaft.

Various air overpressure control measures should be proposed by the Contractorto suit his intended work programme and scheduling of the works.

Allowable Charge Weight (kg/delay)

Distance6.00 5.00 4.00 3.00 2.00 1.00 0.50 0.25 0.10

dBL


23/402


5.5 FUMES AND DUST

Fumes generated from the initiation of explosives can be easily alleviated withproper ventilation. The general philosophy includes:

ensuring adequate ventilation to dilute the fumes, and

ensuring adequate time after blasting before allowing access to the blastface.

5.6 FLYROCK

It is envisaged that flyrock is unlikely to be a problem for the works, as all theblasting will be underground and well below the ground level, and the blast holeswill be well-confined. In addition, a suitable blast face cover will be provided tocover the shaft during each blast. The typical blast face cover is shown inDrawings MCSJV/TW/I-2/2020119 and MCSJV/TW/I-2/2020120 in Appendix L.Flyrock containment measures will be included in Method Statement andsubmitted separately for approval by MD/GEO.


24/402


6.0 OVERVIEW OF SENSITIVE RECEIVERS

6.1 GENERAL

Sensitive Receivers are anything that may be damaged by blast vibrations ornoise. The common sensitive receivers are structures such as buildings andbridges, man-made slopes and retaining walls, natural slopes, and services.Maximum allowable vibration limits have been allocated for these receivers andmaximum charge weights calculated accordingly.

The sensitive receivers, except for man-made slopes and retaining walls, within

a calculated radial distance of the areas to be blasted have been assessed todetermine the maximum allowable charge weight for any specific point along thetunnel. The limit of inspection has been based upon the 5mm/s contour from theassumed blast charge weight at tunnel level.

It must be noted that 5mm/s is much lower than the threshold level of damage tovarious structures and facilities which is normally over 50mm/sec or higher.However, the condition of the structures will be checked by preliminary visualinspection to ensure that they can tolerate the assessed allowable PPVs whichwill normally be defined as 15mm/sec for buildings or structure or as per theanalysed allowable PPVs for the slopes.

Geoguide 4 Section 5.7.1 states As a general guide, blast vibrations from sub-surface works are normally not potentially damaging at distances of more than50m and only exceptionally at distances of more than 100m. It is not clearlystated whether this is in plan distance or radial distance from the source.

With regards to the designated blast areas of Intake I-2, the blasting zone of


25/402


6.4 METHODOLOGY OF ANALYSIS OF CUT AND FILL SLOPES

The calculation of the allowable vibration limits of existing slopes were basedupon the critical peak particle velocity (PPVc) which was calculated using themethod set out in GEO Report 15. The PPVc for existing soil slope wascalculated from the following formulae:-

PPVc = Kc g/(Ka)

where Kc = the critical acceleration at which the slope has a factor ofsafety of 1.0 against failure for Category II/III features and 1.10

for Category I features (m/s-2)g = the acceleration due to gravity (m/s-2)

= the circular frequency of the ground motion (2f) (s-1)

Ka = the magnification factor

In order to obtain Kc, slope stability analyses were performed with varying valuesof Kc until a FOS of 1.0 was achieved. is dependent on the frequency of the

vibration, which typically ranges from 20-100Hz due to blasting. A frequency of30Hz was adopted, as recommended in GEO Report 15, in the assessment.

For an upgraded slope, the pseudo static factor of safety for the slope has beenadopted as 1.20 or as specified in the desk study information. Figures in GEOReport 15 would be used as reference to calculate these PPVc.

6.5 METHODOLOGY OF ANALYSIS OF RETAINING WALLS

The vibration limits of existing retaining walls are calculated in accordance with


26/402


Loading / Material Parameters Partial Factors

Dead Load 1.0

Imposed Loads (storage, residential, etc) 1.0

Transient Loads considered as surcharge in HongKong (traffic, pedestrian loads, etc)

1.0

Water Pressure 1.0

tan where is angle of shear resistance includingbase friction angle (tan b)

1.1

Soil apparent cohesion, c 1.2

Table 6.5: Partial Factors applied to loading and material parameters

The critical PPV is then calculated from the formula shown above in section 6.4.6.6 DESK STUDY

A desk study search of all the various relevant existing man-made features hasbeen carried out. For any DH order features that had not completed upgradingworks, further assessment would be performed to determine whether the chargeweight might need to be reduced to minimize the vibration effect on the features.The desk study results of the adjacent man-made features are summarized and


27/402


performing adequately.

6.8 EXISTING MAN-MADE FEATURES

A detailed desk study search of all the various relevant existing man-madefeatures for this blasting assessment and a summary of the related data arecontained in Appendix H of this report. The relevant pseudo-static stabilityanalysis for the slope that lies close to the blasting influence zone is also outlinedin this BAR.

As also noted from the desk study results, some DH order slopes have not beenupgraded and they are identified to be outside the blasting influence zone.Hence, their impact to the charge weight is considered to be insignificant.

Where there is no records or where the slope has been served with a DH orderwe have analysed the different groundwater conditions of the slopes. It must benoted that there is significant conservatism in the analysis of the slopes. Wehave also carried out a visual inspection of the slopes and have identified thatthe slopes will be able to accommodate safely an allowable PPV of 5mm/sec.

The locations of the affected man made features are highlighted on the plan asshown in Appendix H. Only Feature No. 7SW-C/C1384 is found within theblasting influence zone and the allowable PPV is given in Table 6.8.

Feature No.Consequence-

to-LifeCategory

Feature Type Predicted PPV(mm/s)PPVc

(mm/s)


28/402


Structure EBS Ref. No. Structural Form

Predicted ppv

(mm/s)

Allowable ppv

(mm/s)

Village House I2-001 Concrete Frame 1 10


Yuen Yuen Institute I2-003 Concrete Frame 1 15


Storage I2-005 Wooden Frame 2 15

Storage I2-006 Wooden Frame 2 15

Village House I2-007 Iron Sheet 2 15

Village House I2-008 Iron Sheet 2 15

Storage I2-009 Iron Sheet 3 15



Shrine I2-012 Concrete Frame 1 15




Grave I2-016 Stone 3 25


29/402




Village House TWDT/S/019 Iron Sheet 3 15


Village House TWDT/S/021 Concrete Frame 2 15


Village HouseTWDT/S/024 Iron Sheet

3 15Lo Wai Road TWDT/S/026 Concrete Paved 5 25

Yuen Yuen Home for the Aged TWDT/S/027A Concrete Frame 3 15

Yuen Yuen Home for the Aged TWDT/S/027B Concrete Frame 3 15

Yuen Yuen Home for the Aged TWDT/S/027C Concrete Frame 2 15

Ship Temple TWDT/S/028 Concrete Frame 6 15

Western Monastery TWDT/S/029 Concrete Frame 3 15



Yuen Yuen Care & AttentionHome for the Aged

TWDT/S/040 Concrete Frame 2 15

Temple TWDT/S/080 Concrete Frame 3 15


30/402


WSD Facility Location Predicted ppv(mm/s)Allowable ppv

(mm/s)

100mm Fresh Watermain Along Lo Wai Road 5 25

Table 6.12: Summary Table of Affected Major WSD Facilities

To facilitate the surface construction works, the above fresh watermain has beentemporarily diverted by the Contractor as shown in drawings MCSJV/SK/I-

2/2103007 to 2103009 in Appendix C.6.13 UTILITY COMPANIES

Utility companies have numerous assets crossing and adjacent to the proposedIntake I-2. The services include gas pipes, electricity cables, telephone cables,cable television services, stormwater drains and sewage pipes.

The utilities present within the Intake I-2 blast area are fresh watermains, andtelecommunications ducts; all of which run parallel to Lo Wai Road on the

western side of the existing bridge and come closest to the proposed blastlocations at the access shaft. All utilities remain at least 10m away from theground level of drop shaft blast area.

Table 6.13 summarises the predicted and allowable PPV.

Utility Location Predicted ppv(mm/s)Allowable ppv

(mm/s)

300mm Drain Along Lo Wai Road 5 25


31/402


Facility Predicted ppv

(mm/s)

Allowable ppv

(mm/s)As-constructed ELS System

(Sheet-pile at Upper Man Access Shaft)6.9 >25

As-constructed Air Vent Shaft 92.1 97

As-constructed Approach Channel 6.8 25

Table 6.14: Summary Table of Other Affected Facilities

The assessment for the above facilities is included in Appendix I for reference.

6.15 CONTROLLING SENSITIVE RECEIVERS

The analysis and assessment of the various sensitive receivers are outlined insection 6.2 ~ 6.14 above.


32/402


7.0 CONSTRUCTION REQUIREMENTS

7.1 PROPOSED BLASTING AREAS

The proposed blast locations have been previously discussed in Section 2.0 ofthis report and include the following:

The commencement of blasting for 5m, from a depth of approximately 25mbelow ground level, within a single 5m ID Vortex Drop Shaft which has atotal depth of approximately 30m,

A De-aeration Chamber of approximately 21m long by 9m wide by 13m high, A 3.5m ID Man Access Adit (Lower),

A 4.5m ID Main Adit,

A 4m ID Man Access Shaft (Lower),

A 3.5m ID Man Access Adit (Upper), and

The commencement of blasting for 14m, from a depth of approximately 25m

below ground level, within a single 4m ID Man Access Shaft (Upper) whichhas a total depth of approximately 39m.

As mentioned in the scope of the report and sections 4.0 and 5.0, adetermination of the maximum charge-weight to be used to achieve acomparable advance given the construction constraints was determined basedon preliminary blast designs for the shafts, adits and tunnels. The maximumcharge weights determined were 0.2kg, 0.33kg or 0.4kg of explosive per delay.


33/402


under the same road closure period of the day but not at the same time.

7.4.1 SHAFTS AT INTAKE I-2

Due to the proximity of the local sensitive receivers in the area, including theshaft sound barrier structure itself, low charge weights will have to be used tocomply with the restrictions on allowable PPVs at this location.

Setting up of adequate protective measures will also be required before anyblasting will be able to take place. Due to the location of the shaft, blasting mayhave to be sequential within the blast area as PPVs are restricted to the design

PPV contour due to the proximity of numerous sensitive receivers in the area.This will call for a lowering of the specified charge weights which in turn willdictate the rates of advance in the shaft.

At a predetermined distance, relaxation of the PPV restrictions will allow for fullproduction, i.e. maximum round length with maximum charge weight, as the aditswill then be advanced towards the de-aeration chamber.

As the blasting works approach holing, the advance rate will be reduced again

due to the local PPV limitations and will remain in force until breakthrough.7.4.2 AS-CONSTRUCTED AIR VENT SHAFT

The Air Vent Shaft connecting the De-aeration Chamber to the ground surfacehas already been constructed. The shaft is approximately 30m in depth and issteel lined. The blasting design of the chamber near the shaft is needed to bemodified in order to prevent the shaft from damaged.

The maximum allowable charge weight for the De-aeration Chamber has been


34/402


7.4.4 TUNNEL BLASTING PROCEDURE

(A) Ordering & Delivery of Explosives

To receive explosives from the Kowloon ExplosivesDepot (KED), the Contractor will submit required application for a RemovalPermit to the nominated explosives supplier. Once the order arrives at site, theShotfirer will unload the loading delivery truck and check the order and arrange

for the explosives to be conveying to the blasting face.

(B) Pre-drilling Works for Blasting Surfaces

Pre-drilling works of the blast holes in the shafts and adits will be performedusing a drilling rig and pneumatic rock drills.

(C) Transportation of Explosives down the Shaft using the 20Ton or 15TonGantry

Explosives cartridges will be placed, under the supervision of the Chief Shotfireron wooden boxes specially dedicated for the conveyance of explosives. All theboxes will be locked before conveyance down to blast area level. The firstoperation will be to convey the explosives boxes down the shaft under the


35/402


and reduce the chance of explosive being ejected out of the hole when the

charge is initiated. The stemming will also help to reduce the air overpressure(AOP) levels.

(E) Site Clearance and Evacuation Procedures

Based on the discussion and agreement with TMLG, temporary road closure, ifrequired, will be for carrying out when blasting works at Intake I-2 is required.

All personnel shall evacuate from the shaft and adit. For safer operation, whenthe blast of the Main Adit is within 10m from the Main Tunnel, the area of theMain Tunnel 20m from either side of the interception with the Main Adit will beevacuated.

Except the registered Shotfirer and his assistant, nobody is allowed to stay nextto the Shafts. An evacuation procedure shall be followed. For better protection tothe registered Shotfirer, the Shotfirer shall fire the shot next to the containerwhich is a standard steel-made container near the site entrance.

It is proposed to temporarily close Lo Wai Road and footpath in the vicinity ofshafts for each individual blast for circa 10 ~ 15 minute when blasts are fired.

(F) Covering of Blasting Works

ICE approved noise enclosure structure had been constructed at ground level


36/402


Pedestrians and Public. The PRN will be advising the blasting time and location

as well as clearance areas in advance. The Gong Men and Sentries arepositioned to ensure that the public is not started by any underground shaftblasting in the urban area.

Temporary road closure will be realized until it will be demonstrated that anyAOP effects near the shafts are minimal and that motorists and pedestrians canuse the road safely without being affected by the blasting operation.

A flow chart of the general blasting activities has been included in appendix J forreference.

The details of blasting sequence, evacuation criteria, public and traffic control,checking for misfire, re-entry to tunnel and tunnel support for the shafts, aditsand de-aeration chamber will be further described in the Method Statement.


37/402


8.0 BLASTING CONTAINMENT AND CONTROL MEASURES

8.1 BLAST RESTRICTIONS AND CONTROL LEVELS

It is proposed that Alert, Action and Alarm levels are attached to each productionblast to ensure adequate control. The following actions should be taken if a blastexceeds the specified limit for blast vibration monitoring points for controllingsensitive receivers near to the shaft entrances.

Blast Vibration Control Procedure.

Control

Level

SensitiveReceiver PPV

LimitControl Procedures / Requirements

ALERT PPV> 90%

Inform the RE, Project Manager, DSD Supervisor of occurrence.

Review monitoring data and recording equipment for accuracy.

Check secure placement of transducers.

Review blast pattern and parameters.

Inspect sensitive receivers affected. Prepare action plan.

Continue blasting.

ACTION PPV > 95%

Inform the RE, Project Manager, DSD Supervisor, GEO (MD) immediately.

Review/modify blast pattern and blast parameters.

Review and implement action plan if necessary.

Detailed inspection of all affected sensitive receivers.

Plan and prepare remedial works if necessary.


38/402


iii. To show that the resulting ground vibrations are within acceptable limits

and will not adversely affect the safety or stability of adjoining structures,services and slopes, and the specified tolerances for the works can beachieved.

During the initial blasts at Intake I-2, the practice to be adopted will call for theimplementation of the blast monitoring procedures outlined in Sections 8.3 ~8.7below.

Should the resultant PPVs or airblast levels exceed the limits predicted basedon the approved GEO formula, then a reassessment of the blasting constants tobe used at the Intake I-2 will be required. This will entail an adequate number oftrial blasts, as agreed with the Mines Division, so that determination of the sitespecific blasting constants can be achieved. Continued monitoring will verify anyre-evaluations made.

The same procedure will be adopted during the commencement of blastingoperations at either of the two shafts at Intake I-2. Within close proximity of theblast area of the intake are a number of high ranking sensitive receivers

restricting the PPV values allowed which will call for an increased number ofmonitoring points leading to close scrutiny of the site specific blasting constantsto be applied.

Re-evaluation of the blast constants is essentially an ongoing process where anychanges to blasting regimes, such as the Contractors change to the his blastdesign, an increase in charge weights, length of round, number of blast locationsetc, will require a re-assessment of the blasting constants to be applied.

8.3 BLAST MONITORING


39/402


monitoring purposes. It is expected that there will be some tolerance on this

target based upon the public perception and the level of complaints received onthe actual observed air overpressure effects. Readings and any AOPs exceededwill be assessed on a case by case basis due to the difficulties of predicting air-overpressure and environmental factors such as wind.

8.6 BLAST MONITORING REPORTING

Prior to blasting the Contractor shall provide a Blast Monitoring Report forapproval to the Engineer identifying the blast location and the monitoring pointsof the controlling sensitive receivers to be monitored.

The report shall describe the current status of the controlling sensitive receiversand clearly identify any relevant observations that would reduce or constrain thedesign blast charge weights prior to blasting.

After the blast the Contractor shall produce a short report containing details ofthe actual blast design and the monitoring results showing vibration and airoverpressure readings highlighting any allowable limits that were exceeded.

The report shall also provide reference to the inspections carried out to verify theperformance of the existing slopes, boulders and nearby sensitive receivers andany proposed remedial measures necessary to ensure the safety of the works onthe surrounding area. Any corrective actions or follow up requirements orcomplaints from the general public shall also be noted in the report.

The Contractor shall provide examples of the reports to be submitted to theEngineer for agreement prior to commencing the blasting works.

Blast vibration response spectra shall also be provided with respect to the three


40/402


Most manufacturers recommend detonation as the safest way to destroy

explosives. If detonation is not possible, the options are: Detonators must be detonated in a charged blast hole. They will not be

destroyed by burning or by mechanical means.

Cast boosters and detonating cord will be destroyed in charged blast holeaccording to the MIC.

Electronic detonator will be destroyed on site following the manufacturersrecommendations as stated in their MSDS sheets.

Only qualified personnel (Registered Shotfirer) should undertake destructionprocedures.

All safety procedures recommended by the manufacturer should be followedin the destruction of the explosives.

8.8.2 LOADED BLASTHOLES NOT BEING FIRED ON THE DELIVERY DAY

When unforeseen circumstances happen resulting to loaded explosives unable

to be discharged on delivery day, the following procedure would be adopted priorto the next working day when the firing is possible.

The Blasting Engineer shall inform the Mines Division, BCS, the Police andthe relevant government departments of the unforeseen circumstance and theblasting delay.

The non-blasted area shall be fenced up with colored ribbon stripe and at fourcorners hoisted with red flag indicating this being a danger zone and nobody


41/402


movement/vibration evidence), undisturbed ground or material is observed

within the blast during the detonation or upon inspection, cut offs oruninitiated explosives are observed.

If lead wires, detonating cord or signal (shock) tube is exposed in a portion ofa blasthole that was intended to have been fired, that blasthole will be treatedas a misfire. If there is a doubt as to whether a signal tube has initiated, ashallow angled cut into the tube to examine the inner surface of the tube forevidence of uninitiated explosive composition should be made.

Identification of un-detonated explosives after the all clear has been givenand site work has recommenced.

For all blast-induced incidents, the licensee shall submit to Mines Division aninvestigation report within 5 working days.


42/402


9.0 BLASTING PROTECTIVE AND PRECAUTIONARY MEASURES

9.1 BLASTING PROTECTION MEASURES

For the purposes of blasting operations all measures shall be taken to protectpersons and property from the dangers normally associated with blastingoperations.

Drawings MCSJV/TW/I-2/2020119 and MCSJV/TW/I-2/2020120 in Appendix Loutline the expected measures required during blasting operations at Intake I-2blast area

9.1.1 BLAST PROTECTION MEASURES AT INTAKE I-2

Blast protection measures will be required to protect those works that are withinthe immediate vicinity of the blast area.

Protection measures could include but not be limited to the following:

Blast doors at the top of the shaft,

Blast barricades

Blast mats made of heavy flexible materials such as rubber or rope to placeover any parts of the blast area prior to blasting.

Noise Enclosure to reduce the magnitude of AOP

9.1.2 BLAST PROTECTION MEASURE WITHIN ADIT CONNECTIONS

As the adit connection advances and full face blasting operations take place, theneed for blast protection will generally decrease but there may be the odd


43/402


The predicted AOP induced to the sensitive receivers within the influence zone

of blasting operation are summarized as below.Structure (EBS

Ref. No.)AOP Induced (Before

ReductionFinal AOP (After Reduction)

Lo Wai Road(TWDT/S/026)

130.1 110.1

Ship Temple(TWDT/S/028)

131.5 111.5

Table 9.1.3: AOP Generated to the Sensitive Receiver

9.2 EVACUATION AND CLEARANCE REQUIREMENTS

In addition to the requirements of section 9.1 above, the Blasting Engineer alongwith the Chief Shotfirer will liaise with the Supervising Officer and DSDSupervisors and other stakeholders and give the final permission to blast.

The standard evacuation procedures will be followed for all blasts:

i. Notices will be posted at the site entrance and on boards visible to the roadusers advising the date and expected time of each blast.

ii. After all protective measures have been placed, explosives loading willcommence and tunnel / shaft clearance procedures will be initiated by theShotfirer.

iii. The Shotfirer will inform the Chief Shotfirer / Blasting Engineer and theContractors Site Agent by radio that blasting will take place within thirty


44/402


Evacuation is required and evacuation procedures will be developed in method

statement.9.3 OUTLINE BLAST DESIGNS

The outline blast designs are attached in Appendix G for information. Daily blastdesign will be submitted to Mines Division for blasting operations. Outline blastdesigns and typical daily blast designs will be detailed in method statement.

9.4 PROGRAMME AND DEMAND FOR EXPLOSIVES

A tentative schedule and demand of explosives has been prepared and includedin Appendix J of this report. The programme and demand for explosives will bebased upon the final Method Statement and the quantities of high explosives thatcan be delivered to the shaft and entrances to the works.

The allowable delivery quantities given in the Method Statement will also dictatehow many working faces can be worked any one time if emulsion is not allowedat the lower charge weights.

The demand for explosives has been based upon the estimates number of blasts

that are required to complete the Works. A preliminary assessment estimatesthat 206 numbers of blasts will be carried out during the excavation of Intake I-2.The number of blast for different section has been summarized below.


45/402


Section By length(mPD)/Ch (mPD)/Ch (m) Pull (m) Blast No.Upper ManAccessShaft

+82.5 +68.6 13.9 0.5/0.8 24

Upper ManAccess Adit

Ch0 Ch25 25 0.8 32

Lower Man

AccessShaft

+70 +56 14 0.8/1 15

Lower ManAccess Adit

Ch0 Ch5 5 1 5

VortexDrop Shaft

+74 +69.9 4.1 0.5/1 7

Heading inDe-aeration

Chamber

(Refer drawingMCSJV/TW/I-2/2020123

21.3 0.8 27

Bench inDe-aerationChamber

+65.9 +56.9 9 1 9x5=45

Main Adit Ch0 Ch50.4 50.4 1 51Total: 206

Table 9.4: Summary of Number of Blast


46/402


10.0 SPECIFIC SUPERVISION PERSONNEL

The details and implementation of a site supervision plan covering all aspects ofblast execution and post blast actions will be provided by the Contractor as partof his Method Statement. The Contractor shall provide a site supervision plan forthe works to the Engineer and Mines Division for approval prior to blastingcommencing.

In general, the following personnel shall be employed by the Contractor:

Site agent,

Area in-charge,

Competent person under F&IU Ordinance and its associated Regulations,

Registered Shotfirer,

Qualified Shotfirer, and

Area foreman.

The organization chart has been provided in Appendix J and the following is asuggested list of minimum duties for the position of the key personnel.

10.1 BLASTING ENGINEER (COMPETENT PERSON)

The Blasting Engineer is to supervise all blasting activities. He will ensure that allblasting works will be carried out in a safe and efficient manner, and inconformance with the Blasting Assessment Report, Method Statement and theDangerous Good License / Permit. All elements of the drilling and blasting cyclethat could result in any unsafe situation to the public or site personnel will be


47/402


10.3 THE CHIEF SHOTFIRER

He is a Registered Shotfirer, designated internally, to supervise, with the BlastingEngineer and Blasting Designer, all the blasting operations. He will ensure thatthe blasting works are conducted safely and shall be responsible for all blastingworks in the site including selecting blast location, inspection drill holes pattern,installing protection measures, loading explosives together with other shotfirers,arranging site clearance and check blasting results to identify misfires andimplement, with the Blasting Engineer, the remedial measures to treat it. He willoversee all shotfirers work and will act as a central control man during shotfiring

to arrange sequencing blasts if more than one blast is taken consecutively in theblast day.

10.4 THE SHOTFIRER

The Shotfirer is the individual that is responsible for charging the blasthole withexplosives (primer assembly, loading charge, stemming), initiating all blast withinnon electric system and correcting misfires under the supervision of the ChiefShotfirer. He is also responsible for singing the issue Voucher and the removal

permit. The Shotfirer is under the supervision of the Chief Shotfirer.10.5 AREA FOREMAN

He will be responsible working closely with Shotfirer to provide a workableplatform for driller to conduct drilling; arrange plant to clean the free face to floorfor a good heaving shot for the sake of elimination any heavy confinement statusas a result of rock muck blocking in front; the bench top is free from any looserock block pieces that may be blown out horizontally or vertically at front row. Heis also responsible to ensure the public area that needs to be evacuated is


48/402


11.0 CONCLUSIONS

Given the charge weight limits as indicated there will be an effect on thelength of round and hence a limited rate of advance in the shafts for eachblast achieved. This is compounded by the fact that if too many delays areused i.e. blast holes being initiated one at a time; this could lead tomisfires which in turn impede overall progress.

Where the Drawing MCSJV/TW/I-2/2020117 shows depth of 25m andabove, this is in reference to the underground blasting that will be requiredfor the adits and the de-aeration chamber where due to the depth andattenuation of the ground conditions, larger charge weights can be used.However, interpretation of the analysis results suggest that a maximumcharge weight of 0.2kg/0.33kg should be used for the Shafts and ManAccess Adit (Upper) and a maximum of 0.4kg for the Man Access Adit(Lower), De-aeration Chamber and Main Adit to avoid exceeding theallowable PPV limit.

The 5mm/s contour represents the extent of any significant effects of the

blast which is at an approximate distance of more than 15m from eithershaft.


49/402


12.0 RECOMMENDATIONS

It is recommended that if blasting operations are to take place asubstantial damping mechanism is to be implemented that will reduce tooverall effect of airblast and noise.

This could include, but not be limited to the following:

o Rigid well insulated (e.g. with gumpoles underside) shaft doors.

o Swinging timber blast barricades inside shaft

o Enclosed noise barrier over each shaft It is anticipated that there will be at least one blast per day. Therefore

good communications and control of operations will need to be adopted inensuring that the works are co-ordinated and carried out safely.

Prior to blasting operations, detailed condition surveys will be carried outby the Contractor on the existing registered features and existingbuildings within the influence zones shown, particularly those within very

close proximity to the blast sites. Temporary evacuation before and closestructural inspection after blasting may be a requirement.

Elsewhere, regular inspections shall have to be carried out to review andassess any deterioration in the sensitive receivers. Where significantdeterioration is noted an action plan and remedial works shall be put inplace and blasting suspended until the sensitive receiver fixed orconsidered safe to proceed with blasting.

For each blast, vibration control points will need to be specified and shall


50/402

Appendix A

Overall Layout of the Intake I-2


51/402


52/402


53/402


54/402

Appendix B

Geological Section of Intake I-2


55/402

LEGEND OF SOLID AND SUPERFICIAL GEOLOGY

SUPERFICIAL DEPOSITS

Sand Mixed Qd and Qt

Boulders Undivided, mainly dark grey marine mud

Beach rock Marine mud

Clay/silt, sand and gravel; well-sorted to semi-

sortedMarine sand, part silty

Unsorted sand, gravel, cobbles and boulders;

clay/silt matrixUndivided; red, yellow and grey clay, silt, sand and

gravel

Gravel, cobbles and boulders

SOLID GEOLOGYCourse ash crystal tuff

Fine ash tuff (within Yim Tin Tsai Formation)

Fine ash vitric tuff

Fine-grained granite, 2mm

Fine ash to coarse ash tuffs, tuff-breccia and

tuffite

Fine to medium-grained granite

Coarse ash crystal tuff

Medium-grained granite, 2-6mm

Eutaxite Coarse-grai ned granite, >6mm

Sandstone Fine-grained quartz syenite,


56/402


57/402


58/402

Appendix C

Reference Drawings for Intake I-2


59/402

Drawing ListProject

Page No.Job No. 0 7 2 5 7 W G

Temporary Works Design for Intake I-2

Permanent Works Design for Intake I-2

MCSJV/PW/I-2/2020021

1/2

Intake I-2 Temporary Works Design Temporary Support General Arrangement

Intake I-2 Air Vent Shaft (Upper Part) General Arrangement and Reinforcement Detail

Intake I-2 Man Access Shaft (Upper Part) General Arrangement

Intake I-2 Permanent Works Design Underground Structures and Shafts General Arrangement

MCSJV/TW/I-2/2020030



D



Intake I-2 Permanent Works Design Vortex Drop Shaft General ArrangementD

A

A

A

C

Intake I-2 Permanent Works Design Typical Connection detail between Main Tunnel & Main Adit Plan and Section

Intake I-2 Permanent Works Design Man Access Shafts General Arrangement

Design and Construction of Tsuen Wan Drainage Tunnel

C

B

A Intake I-2 Vortex Shaft (Upper Part) General Arrangement (Sheet 2 of 2)

C

Intake I-2 Vortex Shaft (Upper Part) General Arrangement (Sheet 1 of 2)MCSJV/PW/I-2/2020001

Drawing TitleRevDrawing No.

Intake I-2 Permanent Works Design For Main Tunnel & Main Adit Connection Section



A


Intake I-2 General Arrangement and Layout Plan of Connection between Main Tunnel & Main Adit

Intake I-2 Temporary Works Design Temporary Support DetailsMCSJV/TW/I-2/2020031

MCSJV/PW/I-2/2020023 C Intake I-2 Permanent Works Design De-aeration Chamber General Arrangement

MCSJV/PW/I-2/2020024 D

MCSJV/PW/I-2/2020025 H Intake I-2 Permanent Works Design Air Vent Shaft General Arrangement

MCSJV/PW/I-2/2020026 E Intake I-2 Permanent Works Design Man Access Adit General Arrangement


60/402

Drawing ListProject

Page No.Job No. 0 7 2 5 7 W G

Design and Construction of Tsuen Wan Drainage Tunnel

2/2

Drawing No. Rev Drawing Title

Permanent Works Design for the Approach Channel along the streamcourse

MCSJV/SK/I-2/2104067 A Intake I-2 Concrete bund walls

MCL/4111CD/S/223 A Intake I-2 Sections & Reinforcement Arrangement (with mark-up) x 2

Permanent Works Design for the As-constructed H-pile wall along the streamcourse

MCSJV/SK/I-2/2104068 A Intake I-2 Concrete bund walls (Stage 1)

MCL/4111CD/S/220 A Intake I-2 Structure Lower Level Reinforcement Arrangement (with mark-up)

MCL/4111CD/S/209 A Intake I-2 Details of H-pile Wall

DC/2007/12/SK/0056 D H-pile wall details (Pile cut-off level higher than formation level) in Intake I-2

MCSJV/SK/I-2/2103007 A Intake I-2 Temporary Diversion of WSD Pipe

Drawings for Temporary Diversion of WSD pipe

DC/2007/12/SK/0068 B Revised Pile Wall Layout and Setting Out at Intake I-2

DC/2007/12/SK/0149 B Proposed River Channel Formation Level at Intake I-2

MCSJV/SK/I-2/2103008 B Intake I-2 Temporary Diversion of WSD Pipe Steel Work Support Detail

MCSJV/SK/I-2/2103009 A Intake I-2 Temporary Diversion of WSD Pipe On Grade Fixing Details: Support I

MCSJV/SK/I-2/2103011 A Intake I-2 Temporary Diversion of WSD Pipe Layout Plan


61/402


62/402


63/402

FOR INFORMATION ONLY


64/402


65/402


66/402


67/402


68/402


69/402

FOR I


70/402


71/402


72/402


73/402


74/402


75/402



76/402


77/402


78/402


79/402


80/402


81/402


82/402


83/402


84/402

FOR


85/402


86/402


87/402


88/402


89/402



90/402


91/402


92/402


93/402


94/402

FOR INFORMA


95/402

FOR INFORMA

FOR INFOR


96/402

FOR INFOR


97/402


98/402


99/402



100/402

Contract Doc Vol 4 of 11 Page 166 of 284


101/402



102/402



103/402


104/402


105/402


106/402


107/402



108/402


109/402



110/402



111/402



112/402



113/402

Appendix D

Rockhead and Groundwater Contours Plan


114/402


115/402


116/402


117/402

Appendix E

Inventory of Existing Buildings


118/402


119/402


120/402


121/402

Appendix F

Drawings of Existing Utilities


122/402


123/402


124/402


125/402


126/402


127/402


128/402


129/402


130/402


131/402


132/402


133/402


134/402


135/402


136/402


137/402


138/402


139/402


140/402


141/402


142/402


143/402


144/402


145/402


146/402


147/402


148/402


149/402


150/402


151/402


152/402


153/402


154/402


155/402


156/402


157/402

Appendix G

Typical Blast Patterns


158/402


159/402


160/402


161/402

Appendix H

Assessment of Affected Man-madeSlopes and Retaining Walls


162/402

dSite

tobe


163/402

'

c'

'

-

-

-

Para

meterswerederivedfromlaboratorytestinfresults.

-

-

-

Para

metersforCollandCDTwereadoptedbasedonlaboratorytestingresultsfrom'Ho

mefortheAged

Form

ation(1994).ParametersforFillwereassumed.

-

-

-

Labo

ratorytestingresultsfrom'WesternMon

asteryDevelopment'forFillrevealedfrict

ionangleof33.

Para

metersforCollwereassumed.

-

-

-

Para

metersforFillwereassumed.

-

-

-

Para


35

6

36

Para

menterswerederivedfromlaboratorytestinfresults.Laboratorytestingdatasfoun

d.

-

-

-

Pres

criptivemeasures

-

-

-

Pres

criptivemeasures

-

-

-

Para

metersforFillwereassumedandthefillisassumedtobederivedfromCDG.

-

-

-

Para

metersforfillwerederivedfromlaborato

rytestingresults.ParametersofAlluvium

wereassumed

thesameasFill.

-

-

-

Noa

nalysishasbeencarriedout

35

-

-

Para

metersofc'=0&f'=33wereadoptedforF

ill/Alluviumandc'=1&f'=35forC/HDGd

basedonthe

labo

ratorytestingresults.Laboratorytestingd

atasfound.

-

-

-

Stab

ilityAnalysiscarriedoutinEmpiricalAppr

oach.

-

-

-

Para


S/P

Highest

Recorded

-

-

GWMonitoring

Device

Remarks

GeotechnicalReportforthe

sRoadforYuenYuenCare&

onHomefortheAged'

Remarks

Remarks

HDGd


164/402


165/402


166/402


167/402


168/402


169/402


170/402

15

20

25

Q

6

9.75

7.70

6.41

0.200

8

12.52

9.89

8.24

0.330

0

13.78

10.8

9

9.07

0.400

0

13.78

10.8

9

9.07

0.400

0

13.78

10.8

9

9.07

0.400

15

20

25

Q

6

9.75

7.70

6.41

0.200

8

12.52

9.89

8.24

0.330

8

12.52

9.89

8.24

0.330

15

20

25

Q

8

12.52

9.89

8.24

0.330

0

13.78

10.8

9

9.07

0.400

0

13.78

10.8

9

9.07

0.400

13

15

20

25

Q

6

14.08

12.5

2

9.89

8.24

0.330

6

14.08

12.52

9.89

8.24

0.330

2

15.50

13.78

10.89

9.07

0.400

2

15.50

13.78

10.89

9.07

0.400

2

15.50

13.78

10.89

9.07

0.400

2

15.50

13.78

10.89

9.07

0.400

2

15.50

13.78

10.89

9.07

0.400

2

15.50

13.78

10.89

9.07

0.400

2

15.50

13.78

10.89

9.07

0.400

2

15.50

13.78

10.89

9.07

0.400

2

15.50

13.78

10.89

9.07

0.400

2

15.50

13.78

10.89

9.07

0.400

2

15.50

13.78

10.89

9.07

0.400

2

15.50

13.78

10.89

9.07

0.400

PPV


171/402

PPV Calculation for Existing Slopes/Retaining Wall


172/402

Project

TWDT Bl i A


173/402

TWDT - Blasting AssessmentLocation Approved by Page

Feature Checked by /

Rev.

Calculation of critical peak particle velocity for feature 7SW-C/C1384 at Lo Wai

critical peak particle velocity, PPVc = Kc g / (w Ka)

From SLOPE/W,

Kc = 0.21 with FOS = 1.102 for feature 7SW-C/C1384 (Cat I feature)

where y = 4 and y/H = 1.00

From Figure 8 of GEO Report No. 15,

when S/H = 75.00 where slope height, H = 4 m and S = 300 m/s

Ka = 1.23

g = 9.81

w = 2 x pi x f = 188.50 /s where f = 30 Hz

Therefore, PPVc = (Kc * g) / (w Ka) 8.89 mm/s

Max. PPV from PPV contour is 5 mm/s OK!

Lo Wai

7SW-C/C1384


174/402

Appendix I

Assessment of Existing Facilities


175/402

Sheet-pile (Above Upper Man Access Shaft) Check


176/402


177/402


178/402


179/402


180/402


181/402


182/402


183/402


184/402


185/402


186/402


187/402


188/402


189/402


190/402


191/402


192/402


193/402


194/402


195/402


196/402


197/402


198/402

Existing Air Vent Shaft Check


199/402


200/402


201/402

Appendix J

Explosive Quantities, Delivery Schedule and

Organization Chart


202/402


203/402

Organization and Flow Chart

for Blasting Works


204/402


205/402

8/7/2019 BAR

BAR RevA Resubmission - 24 Dec 2010

Documents

Transcript of BAR RevA Resubmission - 24 Dec 2010