ADVICE FOR DESIGNING OF CONTROLLED BLASTING PATTERNS...

1

Report On

Rock Excavation Engineering Division CSIR-CENTRAL INSTITUTE OF MINING & FUEL RESEARCH

(Council of Scientific & Industrial Research) Barwa Road, Dhanbad (Jharkhand)

Confidential

ADVICE FOR DESIGNING OF CONTROLLED BLASTING

PATTERNS AT NARAYANPOSHI IRON & MANGANESE

ORE MINES, KOIRA, SUNDARGAH DISTRICT, ODISHA TO

KEEP GROUND VIBRATIONS, AIR-OVERPRESSURE/NOISE

AND FLYROCK WITHIN SAFE LIMITS

JUNE, 2018

*CSIR- INDIA*

CSIR-Central Institute of Mining & Fuel Research (CSIR-CIMFR), Dhanbad-826015

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*CSIR- INDIA*

Team Members Associated with the Project

Dr. C. Sawmliana, Principal Scientist

Sri Aditya Rana, Scientist

Sri R. K. Singh, Sr. Technical Officer (1)

Sri N. K. Bhaghat, Sr. Technical Officer (1)

Sri P. Hembram, Technical Assistant

Dr. M. M. Singh, Chief Scientist

&

Dr. P. K. Singh, Director

Rock Excavation Engineering Division CSIR-Central Institute of Mining and Fuel Research

Barwa Road, Dhanbad-826 015

Jharkhand

*CSIR- INDIA*


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CONTENTS

Page

No.

1.0 INTRODUCTION 4

2.0 BRIEF INFORMATION AND GEOLOGY OF THE MINE 5

2.1 Brief information of the mine 5

2.2 Geology 6

2.2.1 Topography 6

2.2.2 Drainage 6

2.2.3 Vegetation 7

2.2.4 Regional Geology 7

2.2.5 Project Geology 9

3.0 INSTRUMENTS USED FOR FIELD INVESTIGATIONS 10

4.0 FIELD INVESTIGATIONS 11

4.1 Experimental Blasts 11

4.2 Monitoring of Ground Vibration and Air Overpressure/Noise 17

4.3 Study of Flyrock 24

5.0 GROUND VIBRATION AND AIR OVERPRESSURE/NOISE RESULTS 24

5.1 Ground Vibration Results 24

5.2 Air Overpressure/Noise Results 27

6.0 FLYROCK RESULTS AND OBSERVATIONS 28

7.0 ANALYSIS OF GROUND VIBRATION DATA 28

7.1 Assessment of Ground Vibration Predictor Equation 28

7.2 Assessment of Safe Values of Maximum Charge per Delay 29

8.0 SUGGESTED CONTROLLED BLAST DESIGN PATTERNS 30

9.0 ADDITIONAL CONTROLLED MEASURES SUGGESTED FOR VIBRATION AND

FLYROCK

34

9.1 Controlled Measures for Ground vibration 34

9.2 Controlled Measures for Flyrock 35

10.0 CONCLUSIONS AND RECOMMENDATIONS 37

ACKNOWLEDGEMENT 42

ANNEXURE 43


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1.0 INTRODUCTION

Narayanposhi Iron & Mn Mines of M/s Arayan Mining & Trading Corporation

Pvt Ltd. is located at Koira and Kashira villages, in Koira Tehsil under Bonai

Sub-division of Sundergarh District, Odisha. The mines operation was started

in 1945. The Mining Lease (M.L.) area has an undulating topography with a

prominent hillock in the central part of the hill. Intervening valleys exist

between the hillocks. Altitudes vary between 540 m RL (lowest) in the

western portion of the lease to 630 m RL (highest) in the central part of the

lease. The ML has about 185Million Ton Iron ore reserve as per latest geology

study report and it may be enhanced during next geological study. The

mines EC capacity is 3.00 Million TPA Iron ore and 0.036 Million TPA

Manganese ore production.

In order to assess the blasting impacts in the form of ground vibration,

flyrock, noises etc. to the nearby villages of the mine, M/s Arayan Mining &

Trading Corporation Limited awarded a scientific study to the Rock

Excavation Engineering Division (Erstwhile Blasting Department) of CSIR-

Central Institute of Mining and Fuel Research (CSIR-CIMFR), Dhanbad,

Jharkhand. The main objective of the study was to develop safe and

optimum blast design patterns for working within the danger zone keeping

ground vibrations, noise/air overpressure and flyrocks within the safe limits for

the safety of the nearby houses of the village as per the norms set by DGMS.

The Rock Excavation Engineering Division of CSIR-CIMFR carried out field

investigations at the mine during the period of 14th to 17th May, 2018. During

this period, eight experimental blasts were conducted of different working

benches in Quarry-4 and RF Quarry. Blast induced ground vibrations and air

overpressures/noises generated during the experimental blasts were

monitored near the residential houses and important structures in


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Naraynposhias and Kashira villages. Flyrock generated during the trial blasts

were observed and recorded in all the blasts.

This report contains the detailed field investigation, results of the

experimental blasts, analyses of the data recorded and recommendations

for safe and efficient controlled blasting parameters for day-to-day blasting

operations at Narayanposhi Iron & Mn Mines without affecting the nearby

residential houses and habitants.

2.0 BRIEF INFORMATION AND GEOLOGY OF THE MINE

2.1 Brief Information of the Mine

Narayanposhi Iron & Manganese Ore Mines of M/s Aryan Mining & Trading

Corporation Pvt. Ltd. is in the villages of Koira & Kashira and Kathamala RF,

Tehesil Koira, district Sundargarh Odisha. The total lease area is 349.254 Ha.

Mine is in operation since 1945. It is located in the Topo Sheet No. 73 G/1 &

73 G/5 with Latitude : 210 54’ 46.07” - 210 56’ 23.13” North Longitude : 850

13’ 41.16” - 850 14’ 56.56” East.

Narayanposhi Iron & Manganese Ore Mines adopt open cast, fully

mechanized method of mining with drilling and blasting. During the period

of field investigation, two pits are working viz. Quarry-4 and RF Quarry. The

excavation planning during the period of 2018 - 2019 and 2018 - 2020 are

given in Table 2.1 and 2.2.

Table 2.1. The In-situ Tentative Excavation (cum) plan of Iron Ore Zone at

Narayanposhi Iron & Mn Ore Mines Year

Name of

Quarry

Total

Excavation

(m3)

Top

Soil

(m3)

OB/SB/IB

(m3)

ROM (m3) ROM /

Waste Ratio

(cum/cum) Ore (m3)* Mineral reject

(m3)

2018-19 Quarry-3 151833 --- 29799 92235 29799 1:0.244

Quarry-4 1105750 --- 247349 648791 209609 1:0.288

R.F block 1268592 --- 248976 770640 248976 1:0.244

Sub-total 2526175 --- 526124 1511666 488384 1:0.263


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Year Name of

Quarry

Total

Excavation

(m3)

Top

Soil

(m3)

OB/SB/IB

(m3)

ROM (m3) ROM /

Waste Ratio

(cum/cum) Ore (m3)* Mineral reject

(m3)

2019-20 Quarry-3 -- --- -- -- -- --

Quarry-4 1011750 --- 27050 744250 240450 1:0.027

R.F block 1278778 --- 250975 776828 250975 1:0.244

Sub-total 2290528 --- 278025 1521078 491425 1:0.138

Table 2.1. The In-situ Tentative Excavation (cum) plan of Manganese Ore Zone at

Narayanposhi Iron & Mn Ore Mines

Year

Name of

Quarry

Total

Excavation

(m3)

Top

Soil (m3)

OB/SB/IB

(m3) ROM (m3) ROM /

Waste Ratio

(m3/m3) Ore (m3) Mineral

reject

(m3)

2018-19 Quarry-5

130191 -- 114535 14091 1565 1:7.32

2019-20 98431 -- 82777 14089 1565 1:5.29

2.2 Geology

2.2.1 Topography

The area is marked by undulating hills with altitudes varying from 545m to

640m above MSL. General slope of the area is towards north on an average.

Three prominent mounds having their highest points at 640m, 620m and

595m are located in the lease area from south to north. Few spurs are

developed in the central portion of the lease area. Another insignificant

mound having peak point of RL 605m occur near Quarry-6. All the above

peak points are connected with each other in different trends with

intervening valleys where from a number of impersistent seasonal nalas

emerge.

2.2.2 Drainage

Drainage system is dendritic type. Two prominent seasonal nalas divided the

whole lease area into three parts from NE to SW which flow due north. River

Karo flowing due north close to the western boundary outside the lease area

constitutes the principal drainage system of the locality and collects surface

run-off water through the seasonal nalas.


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2.2.3 Vegetation

Forest land is of the order of 259.191 hectares which includes 92.113 hectares

reserved forest and 167.078 hectares Khesra forest. The vegetation comprises

mainly bushy forest and having species like Asan, Amla, Bahada, Chara,

Dhaura, Harida, Dhaman, Jamun, Kendu, Kusum, Mango, Patul, Sal, Semul,

Chhana, Atundi, Muturi & Siali etc. The forest is of open type with density 0.1.

2.2.4 Regional Geology

The lease area forms a part of the famous Horse-Shoe shaped Singhbhum-

Bonai-Keonjhar iron ore belt. Geologically, the terrain forms a part of oldest

Meta sedimentary formations representing the Pre-Cambrian Iron Ore

Group. The Major lithounits identified in the region are schists, tuffs, phylites,

shale and Banded Iron Formations comprising of Banded Hematite Jasper

(BHJ) and Banded Hematite Quartzite (BHQ). At many places these units are

covered by laterite.

The Precambrian rocks of this region were first mapped by Jones in 1936 and

then were subsequently modified by Dunn in 1940. Later on, extensive work

has been done in this region by a host of workers. Singhbhum Granite with

enclaves of older meta-basics and meta sedimentary rocks. The structural

set-up of the entire area is a folder plunging synform, with its southern closure

attaining comparatively open nature plunging gently towards NNW.

The effects of the structural deformation in the area are impregnated as

different linear and planner features on the associated litho-assemblages of

this Horse-Shoe belt. The rock of the region have been affected by three sets

of folds of which the effects of first generation folding (f-1) are rarely

preserved, identifiable in localized zones only. This E-W (f-2) fold which is


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superposed by another set of N-S (f-3) folds developing ENE-WSW trending

axial planes. These folds plunge to the ENE as well as WSW at moderately

steep angles. This superposed folding has resulted in formation of a number

of dome & basin structures in the area. The older rocks are exposed in the

domes while the basins preserve the entire stratigraphy. The effect of third

generation of folding (EW) is limited to the younger rocks and has resulted in

the development of E-W axial planes.

The region stratigraphy of the area based on earlier works can be framed as

follows:

Kolhan Group Sandstone, Conglomerate – Breccias

--------------------------------------- Unconformity --------------------------------------

Mixed Facies Basic lavas, tuffs and tuffites of volcanic

facies.

Iron, Manganese, lenses of Iron formation,

chert, small dolomite of chemical facies.

Minor lenses of sandy and silty shale of clastic

facies.

Banded shale formation Banded shale Black shale

Koira Group :

Banded Iron Formation Black shale-chert

Finely banded Jaspillite (BHJ) Coarsely

banded Jaspillite (BHJ)

Volcanic sandstone Tuffaceous shale, Basic Lava Gritty sandstone,

quartzite Conglomeratic at places with inter-

bedded lava at top.

--------------------------------------- Unconformity --------------------------------------

Mesoscopic folds of upright or slightly overturned nature are observed

mainly in the BHJ and rarely preserved in the banded shale formations.

Several large & minor faults are also observed resulting in three dimensional

discontinuities of the lithounits.


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2.2.5 Project Geology

Narayanposhi Iron and Manganese Ore Mine is in the southern end of the

western limb of the Horse-shoe shaped Iron Ore Range of West Singhbhum-

Keonjhar-Sundargarh district of Jharkhand & Odisha. The rock types found

within the leasehold belong to Banded Iron Formation of Koira Group. The

main litho units mapped in this area are laterite, Banded Hematite Jasper,

shale of different nature and cherty phyllite. Alluvium occupies especially the

low-lying areas.

Based on the field studies, the stratigraphic sequence of different litho

assemblages of the area is interpreted as follows:

Soil & Alluvium

Float ore (with Laterite/Canga ore)

Iron Ore Group Ferruginous laterite

Manganiferous shale with Mn-ore

In-situ Iron Ore (with float at places)

The lithounits of BIF usually trend in a NE-SW to NNE-SSW direction with

westerly dips varying from 20˚ to 70˚and their disposition is outlined below-

Soil & Alluvium : Traverses along and across the leasehold, however, show

that alluvial soil covers a sizeable portion of the area. The alluvium occupies

especially the low lying area. These areas are appeared to be barren where

village site and low yielding agricultural fields are seen.

Ferruginous Laterite: Ferruginous laterites occur as intermediate waste and

capping at places on the in-situ Iron ore horizons having Fe content or less

than 55% and contain both hematite and goethite.


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Float Iron Ore: The float iron ore zones may be considered of two types. The

ores are mostly of massive type with big lumps and occur along with lateritic

horizons. Float zone continues up to 5-7 m from surface level which is seen in

quarry 5 & 6. The second variety of float ore over (+)10 to (-)40mm size with

laterites, which is observed in Quarry-1.

Conga Zone: In the north eastern corner and western part of the area,

conga zones are exposed consisting of boulders, cobbles and pebbles of

iron ores re-cemented by lateritic materials. These materials are seen in and

around quarry-4 (old) & Quarry-5.

In-situ Iron Ore: Below the float ore zone, in-situ ore exists and proved up to a

depth of 60m from surface level. Because of its bouldery nature, it is

sometimes mistaken as float ore. An in-situ ore zone is delineated covering all

in-situ ore working quarries like Q-1,3,4,7 etc. However, on the basis of depth

persistence, in-situ ore zone is delineated around the Q-1, 2, 3, 4, 6 & 7.

Manganiferous Shale: Most of the workable manganese ore deposits occur

within this formation. The shale is mostly ferruginous, grey, and pink in colour

with white streaks. These coloured members do not occur in conspicuous

band rather than they are highly mixed up. Manganese bodies usually occur

on the crest of the domes in the variegated shale formed due to the

superposed folding.

3.0 INSTRUMENTS USED FOR FIELD INVESTIGATION

Ground vibrations and noise/air overpressures induced by blasting were

monitored using portable computer-operated digital seismographs namely

MiniMate, MiniMate Plus of M/s Insatntel, Canada and Mini-Seis of M/s White

Industrial Seismology Inc., USA. All the seismographs are of four channels and


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provided with one tri-axial transducer for monitoring of vibration (in mm/s or

in/s) in three orthogonal directions and one-channel for monitoring of air

overpressure/noise in dB(L) or Pa. All seismographs record vibration in three

directions i.e. Longitudinal (L), Vertical (V) and Transverse (T). They also

record peak frequency of vibration in individual directions and compute the

peak vector sum of vibration.

A Sony make Digital Video Camera was utilised in all the trial blasts in order

to assess the generation and propagation of flying fragments from the

blasting faces, if any.

4.0 FILED INVESTIGATIONS

4.1 Experimental Blasts

During the period of field investigation, a total of eight experimental blasts

with four blasts each were conducted in Quarry-4 and RF Quarry. All the

experimental blasts were conducted with 100 mm blasthole diameter. The

depth of holes in the experimental blasts varied from 3.0 to 10.0 m. Smaller

hole depths were used in the sub-bench and top bench portion where

adjustment in hole depth are required to obtain proper bench height. In

general, bench height of 6 m to 10 m are used. The total number of holes in

the blasting rounds varied from 14 to 105. The burden value used in the

experimental blasts varied between 2.5 to 3.0 m and spacing varied from 3.0

to 4.0 m. Depending on the depth of hole, the explosive charge per hole

varied from 19.44 to 70 kg. The total explosive charge in a blasting round

varied between 675.00 and 6,546 kg. The maximum explosive charge per

delay (holes firing within 8 ms widows) varied from 38.88 to 187.00 kg. Details

of the blast design parameters and explosive loading details are given in

Annexure as Table A1. Views of the locations of some of the experimental

blasts are given in Plates 4.1 to 4.5.


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Plate 4.1: View of the location of experimental blast conducted in bottom

bench of Quarry-4 (Experimental Blast No. B-3)

Plate 4.2: View of the location of experimental blast conducted in Top

Bench of Quarry-4 (Experimental Blast No. B-4)


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Plate 4.3: View of the location of experimental blast conducted in Top

Bench of RF Quarry (Experimental Blast No. B-2)

Plate 4.4: View of the location of experimental blast conducted in 3rd Bench

Quarry-4 (Experimental Blast No. B-8)


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Plate 4.5: View of the location of experimental blast conducted in 2nd Bench

RF Quarry (Experimental Blast No. B-7)

Out of the eight experimental blasts, six blasts were conducted using large

diameter cartridge explosives of 83 mm, 2.78 kg weight of M/s IDL Explosives

Limited as shown in Plate 4.6. The other two blasts were conducted with Site

Mixed Emulsion (SME) explosives of M/s Solar Explosives Limited as shown in

Plate 4.7. Nonel (shock tube) initiation system i.e. Down-the-Hole (DTH) delay

of either of 250 ms or 475 ms and Trunk-Line-Delay (TLD) of 17 ms, 25 ms and

42 ms were used in all the experimental blasts. Diagonal firing pattern was

used in all the blasts. Hole-to-hole delays used were either 17 ms or 25 ms

and for row-to-row delays, 42 ms and combinations of 42 ms, 25 ms and 17

ms were used to provide sufficient delay timing. Sufficient top stemming

column lengths were also maintained for all the holes and they varied from

3.0 to 5.0 m depending on the hole depth. All the holes were packed

properly using drill cuttings and tamping rod. Charging of holes using large

diameter cartridge explosives and SME explosives are shown in Plates 4.8 to

4.9.


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Plate 4.6: View of 83 mm diameter cartridge explosive used

in the experimental blast

Plate 4.7: View of BDS of SME explosives of M/s Solar Explosives Limited


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Plate 4.8: View of charging of holes using SME explosive in Quarry-4

Plate 4.9: View of charging of holes using 83 mm diameter explosive


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4.2 Monitoring of Ground Vibration and Air Overpressure/Noise

Narayanposhi village is located more than 300 m from the working bench of

Quarry-4. Kashira village is also located more than 700 m from the nearest

working bench (top bench) of Quarry 4. Similarly, both Narayanposhi village

and Kashira village are more than 1000 m from the RF Quarry. A labour

camp of temporary structure belonging to the mine is located within 500 m

from the nearest working bench of RF Quarry. Highway, Low Tension Line of

11 KV and labour hutments are also located more than 600 m from working

benches of RF Quarry. Therefore, the following ground vibration monitoring

points were selected during the during period of field investigation.

(1) Near the Church in Narayanposhi village.

(2) Near the house of Sarpanch in Narayanposhi village.

(3) Near Quick Dispatch System, inside Quarry-4.

(4) On the haul road, towards Narayanposhi village.

(5) On the ground of old Quarry No. 6, towards Kashira village,

(6) Near labour camp of the mine.

(7) On the haul road towards Labour hutments.

The distances of ground vibration monitoring points from the experimental

blasting sites varied widely, ranging from 110 to 1040 m. In all the vibration

monitoring points, geophone sensors of the seismographs were fixed firmly

on the ground surfaces using Plaster of Paris. Microphone sensors for

recording air overpressure were also fixed near the geophone sensors.

Views of the different ground vibration monitoring points are shown in Plates

4.10 to 4.21.


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Plate 4.10. View of ground vibration monitoring point near the Church in

Narayanposhi village

Plate 4.11. View of ground vibration monitoring point near the temporary

shops, towards the house of Panchayat in Narayanposhi village


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Plate 4.12. View of ground vibration monitoring point near the

house of Panchayat in Narayanposhi village

Plate 4.13. View of ground vibration monitoring point near the temporary

shops, towards the house of Panchayat in Narayanposhi village


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Plate 4.14. View of ground vibration monitoring point on the haul road,

towards Labour Hutments

Plate 4.15. View of another ground vibration monitoring point on the haul

road, towards Labour Hutments


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Plate 4.16. View of ground vibration monitoring point near Labor

Camp of the mine

Plate 4.17. View of another ground vibration monitoring point near Labor

Camp of the mine


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Plate 4.18. View of ground vibration monitoring point on the floor of

Old Quarry No. 6, towards Kashira village

Plate 4.19. View of another ground vibration monitoring point on the floor of

Old Quarry No. 6, towards Kashira village


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Plate 4.20. View of ground vibration monitoring point on the ground surface

towards Kashira village

Plate 4.21. Closer view of ground vibration monitoring point on the ground

surface towards Kashira village


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4.3 Study of Flyrock

All the blasting events were viewed and recorded using video camera to

observe the sources and any occurrence of flyrock. In order to prevent

occurrence of flyrock, sufficient top stemming column heights were

maintained for all the holes to avoid any premature ejection of explosive

gasses.

5.0 GROUND VIBRATION AND AIR OVERPRESSURE/NOISE RESULTS

5.1 Ground Vibration Results

From the eight experimental blasts conducted during the period of field

investigation, altogether, twenty-nine ground vibration data were recorded

at different vibration monitoring stations. Depending on the distance of

vibration monitoring point from the blasting site as well as the explosive

charge quantity used in the blasting rounds, the magnitudes of ground

vibration data recorded from all the experimental blasts varied between

0.568 and 5.17 mm/s. At three instances, ground vibration data could not be

recorded as the magnitudes of vibrations were less than the pre-set

triggered level of the seismographs i.e. 0.5 mm/s. The distance of vibration

monitoring points from their concerned blasting faces varied between 115

and 1040 m. Details of the recorded vibration and air overpressure/noise

data are given in Table A2 in the Annexure. The waveform reports of all the

ground vibration data recorded are also given in the Annexure.

The magnitudes of ground vibration recorded near the Church in

Narayanposhi village varied from 0.813 to 1.68 mm/s. The distance of

vibration monitoring point near the church from the different experimental

blasting sites at Quarry-4 varied from 613 to 707 m. The highest magnitude of

vibration recorded near the church was 1.67 mm/sec with the


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corresponding dominant frequency of 2.75 Hz. This was recorded during the

experimental blast conducted at 3rd Bench in Quarry-4 (Experimental Blast

No. B-8) where the maximum charge per delay was 187.00 kg and the total

explosive charge in the blasting round was 6546.25 kg. The distance of

vibration monitoring point near the church the experimental blasting site was

690.0 m.

The magnitude of ground vibration recorded near the house of Sarpanch in

Narayanposhi village was 1.40 mm/s with the corresponding dominant

frequency of 3.13 Hz. This was recorded during the experimental blast

conducted at 3rd Bench in Quarry-4 (Experimental Blast No. B-8) where the

maximum charge per delay was 187.00 kg and the total explosive charge in

the blasting round was 6546.25 kg. The distance of vibration monitoring point

near the church the experimental blasting site was 668.0 m.

The magnitudes of ground vibration recorded near the Labor Camp of the

mine varied from 1.25 to 2.86 mm/s. The distance of vibration monitoring

point near the Labor Camp from the different experimental blasting sites at

RF Quarry varied from 300 to 490 m. The highest magnitude of ground

vibration recorded on the haul road, closer to the blasting sites, was 5.17

mm/s at the distance of 155 m. The corresponding value of dominant

frequency was 22.8 Hz. This was recorded during the experimental blast

conducted at Sub-Bench in RF Quarry where the maximum charge per

delay and total explosive charge were 38.88 kg and 875.00 kg respectively.

The dominant frequencies of recorded ground vibration waves from the

experimental blasts varied between 2.25 and 26.8 Hz. The Fast Fourier

Transform (FFT) analyses of all the recorded vibration data were carried out

to obtain the dominant frequency level of vibratory motions. The FFT analysis


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of all the vibration data are given in the Annexure. The FFT analyses revealed

that lower values dominant excitation frequency of the ground vibration (< 8

Hz) were obtained in majority of the cases as Figure 5.1.

Fig. 5.1. Plot of dominant frequency of ground vibration waves with distances of

monitoring point from the blasting sites

The Ground Vibration Standards prescribed by the Directorate General of

Mines Safety (DGMS) in Technical Circular Number 7 of 1997 is given in Table

5.1. Since the dominant excitation frequencies of the ground vibration

waves were less than 8 Hz in majority of the cases, the safe level of peak

particle velocity (PPV) for the residential houses and other important surface

structures present nearby the mine, not belonging to the mine management

has been taken as 5 mm/s. However, for the Labor Camp and other

temporary structures of the mine, the safe level of PPV comes to 10 mm/s.

The level of ground vibrations recorded near the Church, Sarpanch house

and nearby the temporary shops in Narayanposhi village are all within the

safe limit. Similarly, the magnitudes of ground vibration recorded near the

Labor Camp and other structures of the mine are also well within the safe

limit.

0

4

8

12

16

20

24

28

32

319 357 440 490 200 250 300 440 150 300 420 613 468 490 707 155 200 405 145 220 300 115 270 385 430 270 432 668 690

Do

min

ant

fre

qu

en

cy (

Hz)

Distance from the blast (m)


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Table 5.1: DGMS standard (Technical Circular Number 7 of 1997)

Type of structure Dominant excitation frequency, Hz

8 Hz 8-25 Hz 25 Hz

(A) Buildings/structures not belonging to the owner

1. Domestic houses/structures (Kuchcha, brick &

cement)

5 10 15

2. Industrial buildings 10 20 25

3. Objects of historical importance and sensitive

structures

2 5 10

(B) Buildings with limited span of life and belonging to owner

1. Domestic houses/structures 10 15 25

2. Industrial buildings 15 25 50

5.2 Air Overpressure/Noise Results

The air overpressure levels recorded from different experimentall blasts

varied between 100 and 129.1 dB (L). Details of the air overpressure results

are given in Table A2 as Annexure. Based on the USBM Standard for surface

mining (RI 8485) as given in Tables 5.2 & 5.3, the air overpressure level of 134

dB(L) has been considered as safe limit for large scale surface mine blasting.

Table 5.2: Air overpressure limits by USBM for surface mining (RI 8485)

134 dB 0.1 Hz high pass measuring system



105 dB C-slow weighting scale on a sound level meter

(Events less than or equal to 2 – sec duration)

Table 5.3: Typical air overpressure criteria (After Oriard, 2002)

171 dB General window breakage

151 dB Occasional window breakage

140 dB Long-term history of application as a safe project specifications

134 dB Bureau of Mines recommendation following a study of large-scale

surface mine blasting

The level of air overpressure recorded near the different ground vibration

monitoring points are all within the safe level as per international standard.


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6.0 FLYROCK RESULTS AND OBSERVATIONS

In all the experimental blasts, no flying fragments were observed or recorded

in the video of all the blasting events. The throws of the blasted materials

were also controlled and restricted within the blasting area only. The control

on flyrock was achieved mainly by the proper blast design patterns, properly

stemming of holes, use of Nonel initiation system for bottom initiation of

explosive charges as well as supervision of the total blasting operations.

Longer stemming column length of more than 3.0 m was used for blasthole

depth of more than 6 m. Clear free faces were also maintained in all the

blasts so that throw of the materials towards the free face will not be

hindered.

7.0 ANALYSIS OF GROUND VIBRATION DATA

7.1 Assessment of Ground Vibration Predictor Equations

The ground vibration data recorded at various locations during the field

investigations were grouped together for statistical analysis. The empirical

equations have been established correlating the maximum explosive weight

per delay (Qmax in kg), distance of vibration measuring transducers from the

blasting face (D in m) and recorded peak particle velocity (V in mm/s). The

ground vibration predictor equation obtained is given below.

988.0

max

145

Q

DV ………………. (7.1)

Coefficient of Determination = 0.665

Standard Deviation = 0.143

The above equation is site specific and applicable only for the Narayanposhi

Iron & Mn Ore Mines of M/s Aryan Mining & Trading Corporation Limited. Due

to irregular land profile, the lower value of coefficient of determination was


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obtained. However, the equations can be used to compute the safe

maximum explosive weight per delay for various distances of concerned

structures depending upon the sensitiveness and importance of the

structures. The regression plot of recorded vibration data are given in Figures

7.1.

Fig. 7.1: Regression plot of vibration data recorded at Narayanposhi Iron & Mn Ore

Mines of M/s Aryan Mining & Trading Corporation Limited

7.2 Assessment of Safe Values of Maximum Charge per Delay

Based on the analysis of ground vibration data recorded from the

experimental blasts, the dominant frequency values less than 8 Hz were

obtained in majority of the cases. Therefore, the safe values of maximum

charge per delay for different residential houses and structures belonging to

the mine management as well as belonging to the nearby villages of


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Naryanposhi Iron & Mn Ore Mines are determined from the ground vibration

predictor equation (i.e. Equations 7.1) and are given in Table 7.1.

Table 7.1: Safe values of maximum explosive charge per delay at various distances

for different structures from the blasting sites Distance of the

structure from the

blasting face

[m]

Safe values of maximum charge

per delay [kg]

For village houses/structure not belongs to M/s Aryan Mining &

Trading Cor. Ltd.

(PPV : 5 mm/s)

200 43.60

225 55.20

250 68.10

275 82.40

300 98.10

325 115.00

350 133.00

375 153.00

400 174.00

425 197.00

450 221.00

475 246.00

500 272.00

525 300.00

550 330.00

575 360.00

600 392.00

625 426.00

650 460.00

675 496.00

700 534.00

8.0 SUGGESTED CONTROLLED BLAST DESIGN PATTERNS

At Narayanposhi Iron & Manganese Ore Mines of M/s Arayan Mining &

Trading Corporation Ltd., the residential houses and other surface important

structures of the nearby villages are very far from the present working

benches. Narayanposhi and Kashira are the nearest villages from the mine


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which are located more than 300 m (i.e. Danger Zone). During the period of

field investigation, the required production was about 10,000 Metric Ton per

day. In general, the total number of holes per round of blast is about 50 to

60. However, based on the ground vibration data recorded during the

experimental blasts, it was observed that more number of holes can be

blasted in a blasting round without affecting the stability and safety of the

nearby village houses and structures.

Therefore, based on the ground vibration analysis results and observations

made from the experimental blasts, the following blasting zones have been

classified for designing of controlled deep-hole blasting at Narayanposhi Iron

& Manganese Ore Mines of M/s Arayan Mining & Trading Corporation Ltd.

(A) 200 - 300 m from the village houses/structures

(B) 300 – 500 m from the village houses/structure

(C) Beyond 500 m from the village houses/structure

The suggested controlled blast design parameters for safe blasting

operations for the different blasting zones from the nearby surface village

residential houses/structures are shown Tables 8.1. The charge factors used in

the experimental blasts varied from 0.49 to 0. 58 kg/m3. It was observed that

good fragmentations were obtained in all the blasts. Therefore, the explosive

charge per hole have been recommended taking the charge factor as 0.55

kg/m3. The blast design parameters given in the table may be changed

based on the nature of the iron and manganese ore deposits. However, the

recommended maximum charge per delay for the different blasting zones

as given in Table 7.1 should be strictly followed to contain ground vibration

within the safe limit.


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Table 8.1: Suggested blast design parameters for controlled blasting operations near

village houses/structures at Narayanposhi Iron & Manganese Ore Mines Blast Design Parameters Blasting Zone

(Distance of the residential houses from the blasting face)

200 - 300 m 300 - 500 m > 500 m

Blasthole diameter (mm) 100 - 115 100 - 115 100 - 115

Blasthole depth (m) 6 - 10 6 - 10 6 - 10

No. of holes 30 - 50 50 - 100 100 - 150

No. of rows 3 to 4 4 to 5 4 to 5

Drilling Pattern Staggered/Squared Staggered/Squared Staggered/Squared

Burden (m) 2.5 - 3.0 2.5 - 3.0 2.5 - 3.0

Spacing (m) 3.0 - 3.5 3.0 - 4.0 3.0 - 4.0

Sub-drilling length (m) 0.5 0.5 -0.7 0.5 -0.7

Top stemming length (m) 3.00 - 5.0 3.00 - 4.5 3.00 - 4.5

Explosive charge/hole (kg) 25.00 - 60.00 25.00 - 70.00 25.00 - 70.00

Max. Charge/delay (kg) 25.00 - 75.00 75.00 - 270.00 270.00 - 350.00

Total Charge (kg) 750.00 - 3,000.00 1,250.00 - 7,000.00 2,500.00 - 10,500.00

Explosive types 83 mm diameter

cartridge

explosives/SME

83 mm diameter

cartridge explosives/

SME

83 mm diameter

cartridge explosives/

SME

Type of in-hole explosive

and surface hole-to-hole

initiations

Nonel (shock Tube)

initiation

Nonel (shock Tube)

initiation

Nonel (shock Tube)

initiation

For in-hole as well as surface hole-to-hole initiation, non-electric initiation

systems (Nonel/shock tube system) are recommended for controlled

blasting operations in the mine. Bottom initiation should be followed while

charging a hole using Nonel system. No detonating cord should be used for

charging of holes and surface hole-to-hole connections. In the experimental

blasts, 17 milliseconds delay TLDs were used for hole-to-hole initiation in a row

in all the blasts, except in one blast, where 25 ms delay was used. However,

25 milliseconds delay of TLDs have been recommended in place of 17 ms

TLDs, particularly for blasting operations within the blasting zone of 200 to 300

distance from the residential houses/structures of the nearby villages. For

delay between row, the minimum delays should be 42 ms. The suggested

firing pattern for multi-rows holes are given in Figures 8.1 to 8.13.


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Fig. 8.1. Suggested firing pattern of holes for multi-row blasts using 25 ms delay between

Holes in a row and combination of 25 ms and 42 ms delays between rows.

Fig. 8.2. Firing sequence of holes and direction of rock movement obtained in the

Suggested pattern shown in Figure 8.1

Fig. 8.3. The number of holes detonated within 8 milliseconds window along with the

the detonation time obtained in the suggested pattern shown in Figure 8.1


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9.0 ADDITIONAL CONTROLLED MEASURES SUGGESTED FOR VIBRATIONS

AND FLYROCKS

Even though controlled blast design patterns have been suggested for

controlling of ground vibration, flyrock and noise/air overpressure for the

safety of the nearby residential houses/structures, the additional controlled

measures have been suggested for further improvement in safe blasting

operations at Narayanposhi Iron & Manganese Ore Mines of M/s Arayan

Mining & Trading Corporation Ltd. in the following section.

9.1 Controlled Measures for Ground Vibrations

The intensity and characteristics of ground vibration generated from a

blasting source depend upon different parameters such as:

Local geology

Charge weight per delay

Distance from the point of blast

Delay period

Spatial distribution of explosive charge

Confinement

Type of explosive

The confinement of explosive charge such as more burden and spacing

values, deeply buried charge (excessive stemming length) and presence of

blasted material at the face (choked face) generally increase the level of

ground vibration. Explosives having lower borehole pressures also produce

lower vibration than those explosives having higher strength with more

detonation pressure.


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The followings are some of the principal factors that can be taken into

account for reducing blast generated ground vibrations:

Minimizing the explosive charge per delay by reducing drill hole

diameter, blasthole depth, decking the explosive charges in a hole and

initiating them at different times.

Reduce the number of blastholes having instantaneous detonators by

using more number of delay detonators.

Choose effective delay time between holes and rows which avoid wave

interaction and give good rock displacement.

Set the initiation sequence in a way that it progresses away from the

structures to be protected.

Maintain bench height to burden ratio more than two and use

adequate powder factor to decrease over confinement of explosive

charge.

Use the largest possible free face blast area and avoid choked face

blasting.

9.2 Controlled Measures for Flyrock

The following suggestions and recommendations have been made as the

additional precautions for future to control flyrock.

The primary means of controlling flyrock is through proper blast design

and delay timing. The consistency of the burden, specially the front

burden (distance between the first row to free face) must be


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maintained. Bench height to burden ratio less than 1.5 should be

avoided.

While loading a shot, the blaster must be aware of his true powder

factor in terms of the amount of explosive to be charged for the

quantity of rock to be fragmented. Charging of excessive explosive

quantity should be avoided.

The blasting site should always be inspected before marking the holes.

If any clay seams, open joints and bedding planes are present in the

bench, an adjustment should be made in the drilling pattern.

The holes should be drilled in conformity of the face. Wherever

possible, vertical holes should be preferred against the inclined holes.

Before loading, blasting officials should always check the hole depths

and ensure that the holes are drilled as per the blast design.

Any change in the blast design should carefully be considered from

the standpoint of its potential effect on flyrock.

All loosened pieces of the rock from the blasting site should be

cleared before charging.

Statutory provisions should be strictly implemented.

An injury due to lack of blast area security occurs when a person fails to stay

inside a blast shelter or in a protected location or safe distances. Accidents

due to lack of blast area security are commonly caused by the followings

which should be strictly taken care of in all the blasting operations.

Failure to evacuate the blast area by employees and visitors,


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Failure to understand the instructions of the blaster or supervisor,

Inadequate guarding of the access roads leading to the blast area,

and;

Taking shelter at an unsafe location or inside a weak structure.

10.0 CONCLUSIONS AND RECOMMENDATIONS

Based on the results of experimental blasts conducted, observations made in

the field and analyses of the ground vibration data collected, the following

conclusions and recommendations are made for safe and optimum

controlled blasting operations at Narayanposhi Iron & Manganese Ore Mines

of M/s Arayan Mining & Trading Corporation Ltd.

(1) In total, eight rounds of experimental blasts were carried out in Quarry-

4 and RF Quarry with four blasts each in both the quarries. The

blasthole diameter used in all the experimental blasts was 100 mm. Six

experimental blasts were conducted with 83 mm diameter cartridge

explosive of 2.78 kg weight per cartridge and two blasts were

conducted with SME explosives. Nonel (shock tube) initiation systems

were used in all the experimental blasts.

(2) The total number of holes in the blasting rounds varied from 14 to 105.

The burden value used in the experimental blasts varied between 2.5

to 3.0 m and spacing varied from 3.0 to 4.0 m. Depending on the

depth of hole, the explosive charge per hole varied from 19.44 to 70.00

kg. The total explosive charge in a blasting round varied between


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675.00 and 6,546 kg. The maximum explosive charge per delay (holes

firing within 8 ms widows) varied from 38.88 to 187.00 kg.

(3) During the experimental blasts conducted in Quarry-4, blast-induced

ground vibrations and air overpressures/noises were monitored near

the Church, Sarpanch house, temporary shops in Narayanposhi village

and haul road closer to the blasting sites, towards Narayanposhi

village. In one experimental blast, ground vibration was monitored

towards Kashira village. The distances of vibration monitoring points

from the blasting sites in Quarry-4 varied from 150 to 707 m.

(4) During the experimental blasts conducted in RF Quarry, ground

vibrations and air overpressures/noises were monitored near the labor

camp as well as on the haul road, closer to the blasting sites, towards

Labor hutments. In one experimental blast, ground vibration was also

monitored towards Kashira village also. The distances of vibration

monitoring points from the blasting sites in Quarry-4 varied from 115 to

1040 m.

(5) From the nine experimental blasts conducted during the period of field

investigation, twenty-nine ground vibration data were recorded at the

different vibration monitoring stations. Depending on the distance of

vibration monitoring point from the blasting site and the explosive

charge quantity used in the blasting round, the magnitudes of ground

vibration data recorded from all the experimental blasts varied

between 0.568 and 5.17 mm/s.

(6) The magnitudes of ground vibrations recorded near the Church in

Narayanposhi village varied from 0.813 to 1.68 mm/s. The distance of


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vibration monitoring point near the church from the different

experimental blasting sites at Quarry-4 varied from 613 to 707 m. The

highest magnitude of vibration recorded near the Church was 1.67

mm/sec at 690 m distance with the corresponding dominant

frequency of 2.75 Hz. This was recorded during the experimental blast

conducted at 3rd Bench in Quarry-4 where the maximum charge per

delay was 187.00 kg and the total explosive charge in the blasting

round was 6546.25 kg.

(7) The magnitude of ground vibration recorded near the house of

Sarpanch in Narayanposhi village was 1.40 mm/s with the

corresponding dominant frequency of 3.13 Hz. This was recorded

during the experimental blast conducted at 3rd Bench in Quarry-4

(Experimental Blast No. B-8) where the maximum charge per delay

was 187.00 kg and the total explosive charge in the blasting round was

6546.25 kg. The distance of vibration monitoring point near the church

the experimental blasting site was 668.0 m.

(8) The magnitudes of ground vibration recorded near the Labor Camp

of the mine varied from 1.25 to 2.86 mm/s. The distances of vibration

monitoring point near the Labor Camp from the different experimental

blasting sites at RF Quarry varied from 300 to 490 m.

(9) Ground vibration data could not be recorded at the monitoring point

on ground surface towards Kashira village during the experimental

blast in Quarry-4 and RF Quarry. The distances of vibration monitoring

points from the blasting sites at Quarry-4 and RF Quarry were 460 m

and 1040 m respectively.


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(10) The highest magnitude of ground vibration recorded on the haul road,

closer to the blasting sites was 5.17 mm/s at the distance of 155 m. The

corresponding value of dominant frequency was 22.8 Hz. This was

recorded during the experimental blast conducted at Sub-Bench in RF

Quarry where the maximum charge per delay and total explosive

charge were 38.88 kg and 875.00 kg respectively.

(11) The dominant excitation frequency of the ground vibration waves

ranged between 2.25 and 26.8 Hz. Based on the attenuation

characteristic of ground vibration waves and dominant frequencies,

the safe level of ground vibration in term of peak particle velocity

(PPV) for the residential houses/structures of the nearby villages has

been taken as 5.0 mm/s. However, for the structures belonging to M/s

Aryan Mining and Trading Cor. Ltd., PPV value of 10 mm/s has been

taken safe level for ground vibration as per the DGMS Standard

(Technical Circular Number 7 of 1997).

(12) The levels of ground vibration data obtained from the experimental

blasts conducted at Quarry-4 and RF Quarry nearby the different

structures/houses were all within the safe limits as per the DGMS

Standards.

(13) The levels of air overpressures recorded from different trial blasts varied

between 100 and 129.1 dB (L). The magnitudes of air overpressure

recorded were within the safe limits and will not cause structural

damages to the village houses.

(14) No flyrock was observed in any of the experimental blasts. The throws

of the blasted materials were also controlled and restricted within the


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blasting areas only. The control of flyrock was achieved through

proper blast design patterns along with their proper implementation

and supervision of the total blasting operations.

(15) Ground vibration predictor equation have been established for

Narayanposhi Iron & Manganese Ore Mines and is given as Equation-

7.1 in the report. The recommended explosive weights per delay for

various distances from the village houses/structures are given in Table

7.1 in the report.

(16) Based on the analysis results of ground vibration data collected,

experimental blasts results and observations made, the blasting zones

have been classified for controlled blasting operations nearby the

residential houses/structures of the village as:

(D) 200 - 300 m from the village houses/structures

(E) 300 – 500 m from the village houses/structure

(F) Beyond 500 m from the village houses/structure

(17) Details of the suggested controlled blast design parameters for the

different blasting zones are described in Section 8.1 of the report. It is

recommended to use 25 milliseconds delay of TLDs between holes in a

row instead of 17 ms TLDs. The minimum delay between rows should

also be 42 ms.


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Acknowledgement

The research team are thankful to the management of M/s Arayan Mining &

Trading Corporation Ltd. for awarding the study to CSIR-CIMFR, Dhanbad.

They also thankfully acknowledge the sincere cooperation and help

extended to them during the period of field investigation by the following

officials M/s Arayan Mining & Trading Corporation Ltd and M/s Thriveni

Earthmover Private Limited.


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ANNEXURE

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Table-A1: Details of experimental blasts conducted at Narayanposhi Iron & Mn Ore Mines of M/s Aryan Mining & Trading Corp. Ltd, Koira, Sundergarh, Odisha

Blast No.

Date of

blast

Location of blast

Hole dia.

[mm]

Hole depth

[m]

No. of

holes

Avg. Burden

[m]

Avg. Spacing

[m]

No. of

deck

Avg. top stemming

length [m]

Avg. charge/

hole [kg]

Total charge

[kg]

Max. Charge/

delay [kg]

Remarks

B-1 15-05-2018 RF Quarry,

1st

Bench

110 8.5-9.0 40 3.0 3.5 Nil 4.0 - 4.5 48.125 1925.00 100.08 Cartridge explosive with Nonel

initiation system, DTH-475 ms,

TLD-17 ms

B-2 15-05-2018 RF Quarry,

Top bench

110 3.0-6.0 64 2.0-2.5 2.5-3.0 Nil 2.2 - 3.0 8.34

&

22.24

950.00 66.72 Cartridge explosive with Nonel


TLD-17 ms

B-3 15-05-2018 Quarry -4,

Bottom bench

110 6.0 40 2.5 3.0 Nil 3.0 22.50 900.00 45.00 Cartridge explosive with Nonel


TLD-17 ms

B-4 15-05-2018 Quarry-4,

Top bench

110 6.0 30 2.5 3.0 Nil 3.0 22.50 675.00 45.00 Cartridge explosive with Nonel


TLD-17 ms

B-5 16-05-2018 RF Quarry,

Sub-bench

(Top)

110 5.0 45 2.5 3.0 Nil 2.5-2.75 19.44 875.00 38.88 Cartridge explosive with Nonel


TLD-17 ms

B-6 16-05-2018 Quarry-4,

Top bench

110 6.0 55 2.5 3.0 Nil 3.0 22.27 1,225.00 44.54 Cartridge explosive with Nonel


TLD-17 ms

B-7 17-05-2018 RF Quarry

2nd

bench

(Northern

side)

110 9.0 14 3.0 3.5 Nil 4.0-4.5 65.25 913.500 65.25 SME explosive with Nonel


TLD-25ms, 42ms

B-8 17-05-2018 Quarry-4,

3rd

Bench

110 9.0-10.0 105 3.0 3.5 Nil 4.5-5.0 62.34 6,546.25 187.02 SME explosive with Nonel


TLD-17ms,42ms


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Table-A2: Details of ground vibrations, air overpressure and flyrock recorded at Narayanposhi Iron & Mn Ore Mines, Koira, Odisha

Blast No.

Date of

blast

Location of

blast

Total charge

[kg]

Max. Charge /

delay [kg]

Ground vibration results Noise / AOP

[dB(L)]

Flyrock observed; if

any Monitoring points Distance

[m]

PPV

[mm/s]

Freq.

[Hz]

B-1 15-05-2018 RF Quarry,

1st

Bench

1925.00 100.08 On haul road, hill slope towards hutment 319 3.33 11.9 112.0 No flyrock

Near the haul road, hill slope, towards hutment 357 1.70 6.63 112.0

On level ground, near labour camp 440 1.65 9.25 108.4


B-2 15-05-2018 RF Quarry,

Top bench

950.00

66.72 On haul road, hill slope towards hutment 200 4.08 10.1 112.0 No flyrock




B-3 15-05-2018 Quarry -

04,

Bottom

bench

900.00 45.00 On haul road, bottom bench towards Narayanposhi village 150 4.00 7.25 - No flyrock

On ground surface near Quick Dispatch System (QDS) 300 1.43 5.38 128.9

Near the temporary shop, towards Panchayat house 420 2.10 26.8 108.0

Near the Church of Narayanposhi village 613 1.28 5.13 101.0

B-4

15-05-2018 Quarry-04,

Top bench

675.00 45.00 On haul road, bottom bench towards Narayanposhi village 468 0.568 2.75 128.6 No flyrock

On ground surface near Quick Dispatch System (QDS) 490 0.603 7.13 -

Near the temporary shop, towards Panchayat house 584 <0.5 - -

Near the Church of Narayanposhi village 707 0.813 2.63 -

B-5

16-05-2018 RF Quarry,

Sub-bench

(Top)




On ground surface, towards Kashira village 1040 <0.5 - -

B-6

16-05-2018 Quarry-04,

Top bench

1225.00 44.54 Old Quarry No. 6, towards Kashira village 145 3.84 6.7 116.3 No flyrock

Old Quarry No. 6, towards Kashira village 220 1.21 2.25 100.0

Old Quarry No. 6. towards Kashira village 300 1.17 3.25 130.9


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On ground surface, towards Kashira village 460 <0.5 - -

B-7

17-05-2018 RF Quarry

2nd

bench

(northern

side)


Near the haul road ,hill slope, towards hutment 270 4.18 13.5 129.1



B-8

17-05-2018 Quarry-04,

3rd

Bench

6546.25 187.02 On ground surface near Quick Dispatch System (QDS) 270 2.46 6.60 116.9 No flyrock

Near Gate No-2, Narayanposhi Village 432 2.08 2.25 109.5

Near Sarpanch house, Narayanposhi Village 668 1.40 3.13 129.1

Near Church of Narayanposhi Village 690 1.67 2.75 103.5


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EVENT REPORTS AND FFT REPORTS

OF GROUND VIBRATIONS


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ADVICE FOR DESIGNING OF CONTROLLED BLASTING PATTERNS...

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Transcript of ADVICE FOR DESIGNING OF CONTROLLED BLASTING PATTERNS...