Assignment-1,
Subject: Strata Control Technology, MN 6412
Title: Shield support and Strata Behavior Vis-A-vis Geotechnical
Challenges in Longwall Mining: A Case Study
Submitted by
Lalith Kumar
920MN5018
Executive Ph.D
DEPARTMENT OF MINING ENGINEERING
NATIONAL INSTITUTE OF TECHNOLOGY
ROURKELA, ODISHA – 769008
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Shield support and Strata Behavior Vis-A-vis Geotechnical
Challenges in Longwall Mining: A Case Study
Abstract:
Abstract: Longwall mining in the Indian subcontinent has been considered as a
challenging endeavor due to the limited availability of reserves amenable to largescale extraction. Despite these constraints, the Adriyala Longwall Project was
commissioned in 2014 with state-of-the-art high-capacity longwall technology.
Designed for an annual production capacity of 2.8 million tonnes (MT), the project
aimed to demonstrate the feasibility of high-mechanization in Indian underground
coal mining.
Operating under complex and dynamic geo-mining conditions, the mine has
successfully extracted over 15 MT of coal in a decade from a single underground
coal mine, making it the first longwall operation in India to achieve such sustained
production. This success serves as a benchmark for the implementation of advanced
mechanized underground mining in the country.
The study presented in this paper focuses on the strata behavior observed during
the development and extraction of three longwall panels. Key aspects, including
strata control measures, geotechnical responses, and operational challenges, are
analyzed to provide insights into the technological adaptations required for longwall
mining in Indian conditions. The findings contribute to the broader understanding of
longwall strata mechanics and serve as a reference for future high-capacity
underground mining projects in similar geological conditions
Key words: Longwall, Strata control, bolting
The first high capacity longwall face with a state of art equipment, production
capacity of about 3MTPA, panel length of about 2300m and 250m face width was
commissioned in 2014 at Adriyala Longwall project, SCCL, by addressing all the
strata problems encountered in the earlier longwall panels.
This paper mainly focuses on strata control aspects around the longwall face while
extraction of longwall panel at Adriyala Longwall Project.
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Introduction: Longwall mining in deeper deposits under massive strata is a difficult
and well known problem. Face and roof control issues are the main problems
associated with mining under massive strata. A number of longwall mines in INDIA
have experienced severe problems due to strata control issues. It is often not easy to
define exactly which near seam strata controls the roof behavior, but in general
massive strata within the first 50m above the mining seam are considered to have a
significant effect on geo-mechanics of longwall mining.
First longwall mining in INDIA was started in 1978 in Moonidhih colliery. Since then
over past 4 decades it experiences at over 50 longwall faces with shield capacities
up to 800T and production capacities upto 0.6 MTPA. The coal industry is more
depend on other technologies than longwall due to underperformance of longwall
installations including the collapses at Churcha West (1989) and Kottadih (1997).
The main reasons for the underperformance of longwall mining in INDIA are the
inadequate characterization of geological and geotechnical environment, design of
panels and poor selection of shield capacity. The strata control problems not only
hinder the production and productivity but also endanger the safety of persons and
machinery working therein.
The Singareni Collieries Company Limited (SCCL), which is the biggest coal
producing company in south India had the experience of working of low capacity
longwalls of production capacity of below 0.6 MTPA.So far 10 nos Longwall
packages have been introduced in seven mines with collaboration of foreign
countries like UK, and China and face lengths were varying between 95m to 165m,
panel lengths are less than 800m and depth varying from 45m to 360m. In these low
capacity long walls, the gate roadways were developed with conventional road
header and the roof is supported with 1.8 m long cement grouted roof bolts by using
electrical drills. The development rates were slow. The secondary support in the gate
roadways was done by the conventional approach of rope stitching, girders and cogs
etc which are not stiff to arrest increase of rate of convergence and strata problems.
In most of these longwalls, the occurrence of cavities and strata problems were very
common phenomenon in gate roadways and longwall faces due to poor standards of
bolting, instrumentation, monitoring and poor health of powered roof supports in the
longwall face. Earlier, these longwalls were introduced without complete
geotechnical analysis of the strata which created unexpected strata problems while
developing or retreating of longwalls.
With the experiences of earlier longwalls and to meet the coal demand in future,
SCCL has commissioned its first high capacity longwall face with a state of art
equipment, production capacity of about 3MTPA, panel length of about 2300m and
250m face length, in 2014 at Adriyala Longwall project, by addressing all the strata
problems encountered in the earlier longwall panels. Meticulous planning in all the
aspects and detailed geotechnical studies by the reputed scientific agencies were
done for introduction of the technology. Finalized the design parameters with the
technical assistance from scientific agencies like CSIRO, Australia, CIMFR, ISM,
NIRM, IIT-BHU(Indian scientific agencies) for geo-tech studies, panel design,
support capacity, ventilation planning, subsidence prediction etc, Mesy India pvt ltd
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for in-situ stress studies and taking assistance from Australian consultants for mining
operation and strata control aspects.
High capacity longwall technology is the only viable solution for extraction from
deeper deposits of underground mines with high production rates, if properly plan
and executed in view of strata control.
Research gap:
•
In India, research activities in longwall ground control are mainly focused on
numerical analysis, analytical model studies. In a few cases, monitoring of
chain pillars and gateroads are conducted in few longwall panels operated by
SCCL. Numerical studies were conducted to investigate stress distribution
around the chain pillars, face area and gateroad area.
•
An extensive literature review on Indian longwall scenario over the last few
decades suggests that majority of the longwall downtimes and/or failure had
contributed due to ground control problems, inexperience with longwall
technology, inadequate power supports and lack of knowledge about the local
geologic conditions. Some of these problems could have been overcome or
forecasted if proper monitoring of support’s pressure and/or proper analysis
about the roof behavior were performed.
•
However, in India, no study has been conceived thus for based on strata
monitoring data to study the stability of gateroads and longwall panel face
area.
•
no study has been reported on the analysis of cumulative roof convergence
along the gateroads and correlate them with direction of mining.
Novelty:
•
The study presented in this paper focuses on the strata behavior observed
during the development and depillaring of three longwall panels. Key aspects,
including strata control measures, geotechnical responses, and operational
challenges, are analyzed to provide insights into the technological adaptations
required for longwall mining in Indian conditions.
•
The findings contribute to the broader understanding of longwall strata
mechanics and serve as a reference for future high-capacity underground
mining projects in similar geological conditions
Case Study: Salient Features of the Adriyala LW Project
•
•
•
•
•
•
•
•
Workable seams
Gassiness of the Mine
Geological Reserves
Extractable Reserves
Life of the Mine
Depth range
Length of gateroads
Face width of longwall panels
: I, II, III and IV
: Degree-I
: 137 MT
: 78.597 MT
: 35 years
: 294 – 644m (Planning up to 800 m)
: 2700 m to 3000 m
: 250 m
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•
•
•
•
Total Mine area
Seam gradient
Capacity of the mine
Present working seam
: 4.845 Sq. Km.
: 1 in 6 to 1 in 7.8
: 2.817 MT
: No.1 seam
Fig 1: Key Plan showing the longwall panels in ALP mine
Panel
Longwall
Panel No.
I
Longwall
Panel No.
II
Longwall
Panel
No.III
Longwall
Panel No.
IV
Dimension
(Length x
Width) (m x
m)
Depth of
workings
(m)
Gate
roads
length
(m)
Gateroad wise
Min. & Max. depth
(m)
Interconnec
tions
interval (m)
2336 x 250
Min-366,
Max-457
TG-I:
2706,
MG-I:
2784.5
TG-I: Min.-366, Max.414
MG-I: Min.-400, Max.457
200
Dosco Road header
2232 x 250
Min-409,
Max-507
TG-II:
2796,
MG-II:
2858
TG-II: Min.-409, Max.465
MG-II: Min.-433, Max.507
200
Dosco Road header
2429 x 250
Min-445,
Max-556
TG-III :
2871,
MG-III :
2950
TG-III: Min.-445, Max.519
MG-III: Min.-470,
Max.-556
100
Bolterminer
2594 x 250
Min-478,
Max-607
TG-IV:
2972,
MG-IV:
3050
TG-IV: Min.-478, Max.567 MG-IV: Min.-511,
Max.-607
100
Bolterminer
Development
machinery
Geotechnical constraints at ALP: The key geotechnical parameters at ALP for
development of gate roadways and achieving of its rated production from longwall
are as follows:
• High cover depth more than 400 m. (presently working at 600m depth)
• Weak coal roof having RMR of 46 or less.
• Presence of two clay bands in the immediate coal roof.
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•
•
•
•
Need to drive wider galleries (5.5 m width) for gate roadways for about more
than 2.5 km length and 8 m width installation roadway with coal roof
Varying geology in the panels, high water bearing overlying strata.
Influence of horizontal stress and its effect on weak coal roof.
Presence of massive sandstone of thickness more than 20 m as Main roof
resulted periodic weighting.
Fig 2: Bolting pattern with twin on board roof bolters on DOSCO Road header
Fig 3: Convergence status after development of gate roadways
Auditing of gate roadways: Frequent auditing of the gate roads was done to
ensure the condition of the roof and sides and requirement of secondary support.
Basing on the audit report, the response plan was prepared and implemented
immediately. Trigger Action Response Plan for development of gate roadways was
prepared to implement during the development of gate roadways.
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The roof bolting auditing helped in improvement of standard of roof bolting system
with DOSCO on board bolters.
Strata control issues encountered during development and steps taken: During
the development of gate roadways, the following strata control issues were
encountered.
1. Strata problems in cutthroughs: During the initial stages, the cutthroughs were
developed in unfavorable direction with respect to major horizontal stress
direction (SH) caused the severe roof control problems with guttering, more
convergence and also required heavy girder support. The direction of the
cutthroughs were changed or reoriented to drive in favorable direction with
respect to major horizontal stress direction which improved the roof condition
(Fig: 4).
Fig 4: Comparison of strata condition in cut throughs –Effect of SH direction
2. Introduction of rigid weld mesh in place of linked mesh: During initial stages
the roof was supported with linked wire mesh along with W straps. The mesh was
loose and not stiff against the roof and allows the skin failure of the roof and the
bolting cycle was also delayed. The system was replaced with rigid weld mesh
without w straps, which improved the strata condition and also reduces the
bolting cycle time.
Fig 5: Comparison of Roof condition with linked mesh and rigid mesh
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3. Change of working section: The No.1 seam is 6.5m to 7.0m thick having 2 clay
bands. The middle clay is 0.2m to 0.4m thick located about 3.4m from the stone
floor and top clay is 0.7m thick located just below the stone roof. There will be
2.2m to 2.3m parting between two clay bands and having the weak and
laminated coal layers.
During initial stages of development, the middle clay was taken into working
section (Old working section) which resulted in bad roof and more convergence
was observed due to existence of weak and laminated strata in the immediate
roof. The working section was modified by keeping the middle clay above the
1.0m thick immediate roof, which improved the roof condition and reduced the
roof convergence (Fig 6).
Fig 6. Change of working section during development
4. Stress notch effect on TG1: During the development of TG1, it experienced the
Major horizontal stress concentration (Stress Notch) effect due to existence of old
extracted longwalls, which caused the roof detoriation and also high amount of
convergence (Fig 7). Once the zone of major horizontal stress concentration
crossed, the condition of the roadway was improved. This clearly proved that the
existence of Major horizontal stress effect on roadways and resulted to strata
control problems. Further high standards of roof bolting was ensured to keep the
roof stable and convergences were within permissible limits.TG1 was initially
developed with old working section (taken up to middle clay) for about 400m
where high amount of convergence was noticed and the area is additionally
supported with girders.
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Fig 7: Horizontal stress concentration effect on TG1.
Strata Control issues during retreat of longwall panel No1: The longwall panel
no1 retreat was started on 15.10.2014 and the presently meshing is going on. The
monitoring of longwall panel includes the monitoring of gate roads, longwall face and
the goaf.
Convergence monitoring of gate roads: The gate roads were monitored with
convergence stations, Dual height tell tales (2m anchor, 4m anchor) to monitor the
bed separation in the roof as per instrumentation plan (Fig 10).
Fig 10: Instrumentation plan during retreat of LWP No.1
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Fig 11: Convergence in MG1 and TG1.
Observations: From the above the following are observed.
1. The maximum convergence in MG1 is 177mm at 350m from the face start line
when first subsidence noticed at the surface and face retreat was equal to the
depth. In the remaining locations, the maximum convergences were less than
100mm.
2. In TG1, more roof convergence was observed during the retreat of longwall,
where development convergence was more due to poor reinforcement, old
working section and stress notch due to previously worked out longwall
panels.
3. The maximum convergence in TG1 was 276mm in stress notch and old
working section area and the maximum convergence in other area is 37mm.
4. Most of the separation occurred at the top clay located above the bolted zone
and less separation within the bolted zone, indicates adequate strength of
bolted zone and efficacy of the bolting system.
5. The convergence starts increasing when face was 10m to 25m away and
recording maximum when face was reached to the station. Hence, the front
abutment zone was within 25m from the face.
6. The cable bolts effectively controlled the increase of excessive convergence
in the gate roads and no instability was observed in the gate roads during the
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retreat of longwall and no production loss was observed due to strata
problems in the gate roadways.
TG2 convergence: MG1 and TG2 were developed as a twin gate roadway system
and TG2 will be the Tail gate for next longwall.TG2 will experience cyclic and
dynamic loading from development stage to till extraction two successive panels and
chain pillars will be under double goaf effect. The chain pillars will experience five
stages of loading during retreat of longwalls as per Fig 12. The following are the 5
stages of chain pillar loading.





Position a- development loading
Position b –Front abutment loading due to extraction of LWP No.1
Position c – Maingate loading or side abutment loading due to LWP No.1
Position d – Tailgate loading ( Front abutment loading of LWP No.2 and side
abutment loading of LWP No.1)
Position e – Double goaf loading due to extraction of LWP No.1 & 2.
During these stages, the chain pillars will be subjected to loading and TG2 will
experience the convergence accordingly.
Fig 12: Stages in the dynamic loading cycle of longwall chain pillar
Presently, the effect of extraction of longwall panel no1 on TG2 was studied by
installation of convergence stations and tell tales. The TG2 shall be further studied
for effect of longwall panel no.2 retreat. The convergence stations were installed for
every 25m interval and tell tales for every 50m interval. TG2 was supported with
cable bolts as per support plan ( one cable bolt for every 2m interval and at the
junction 9 cable bolts), and additional cable bolts were installed wherever roof is
disturbed and recorded more than 30mm convergence during the development.
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Fig 13: Convergence behavior in TG2 and effect of LW extraction
Observations on TG2 convergence: The following were observed from the
convergence monitoring of TG2 (Fig 13).
1. The maximum convergence was observed 211mm at 340m location from the
face start line when first subsidence noticed at the surface and face retreat
was equal to the depth.
2. The convergence in TG2 is active between 30m to 260m behind the longwall
face and after that it was getting stabilized.
3. The effect of longwall pane no.1 extraction on TG2 was equals to the width of
the longwall face (250m).
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4. Most of the bed separation was noticed at top clay which was above the
bolted zone, indicating the efficacy of bolting system.
5. Resin anchored bulbed cable bolts effectively withstand for the side abutment
load due to longwall panel no.1 extraction and controlled the excessive
convergence in the TG2.
Stress monitoring: The stress cells were installed in longwall pillar and barrier pillar
to monitor the induced stress due to longwall retreat. The maximum stress noticed in
the barrier pillar is 1.78 Mpa whereas in the longwall pillar is 1.7Mpa. The stress was
starts increased when face is 10 to 25m away and recorded maximum when face
reached the station. From the stress and convergence behavior, it was observed that
the front abutment zone was acting up to 25m ahead of the longwall face (Fig14).
Fig 14: Stress behavior in barrier and Longwall pillar
Longwall face monitoring:
Pressure monitoring: The pressures of the shields are continuously monitored
using PMC-R and from the control center at surface. All the data will be transferred
to surface to monitor all the shields pressures across the face and it can store data
for each second. The longwall face was monitored for increase of load by monitoring
the leg pressures of the shields.
Pressure data acquisition with PMC-R: The shields are electro hydraulic operated
with use of PMC-R (Programmable Mining Controller- Roof Support). Each shield is
attached with PMC-R. All the face operations for shield movements shall be done
with the use of PMC-R. The hydraulic legs are equipped with the pressure sensors to
record the pressures. Every second, the signal from the pressure sensor sensed by
PMC-R and the same is transmitted to the underground computer and surface
control center (Fig15). The data will come in log files format and the data from the
log files will be extracted with the help of Manufacturer made software called Vshield
(Fig16).
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Fig 15: PMC-Roof monitoring system of the shields
Fig16: Pressures and face monitoring by Vshield software
Weighting details: During the extraction of the longwall, the immediate coal roof
fallen immediately behind the supports and local falls were observed. During the
local falls of coal, the pressures were not increased in the shields. After 39m of
retreat, first stone fall of height about 1 to 1.5m was noticed in the goaf with sounds
and the pressures were build up but not bleeded.
Main fall: The main fall occurred on 17-12-2014 after retreat of 83m, with area of
exposure of 23205 sq.m. During the main fall, the following were observed.




Breaker line was formed along the face 1-2m ahead of the shields from
20th to 130th shield.
Heavy sound in overlying strata and water seepage of about 250GPm
from the goaf were observed.
Weighting zone observed was 15th to 130th shield ( i.e 115 nos shields out
of total 146 nos shields) and total 75 nos shields were bleeded (Fig 15).
The weighting was cleared after 4 to 6 shears of retreat.
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

Convergence increase of about 36mm/day in MG1 was observed and
guttering on rise side of the gallery up to 15m ahead face, but no effect
was observed on TG1 and TG2.
Rate of stress recorded is 249 KPa/day in the barrier pillar with cumulative
stress was 1.7Mpa.
Fig 17: Pressures across the face during main weighting
Periodic weightings: After main weighting, the periodic weightings were occurring
at regular interval.
Fig 18: Periodic weighting trend in LWP No.1
Observations: Total 154 nos periodic weightings were occurred during 2308m
retreat of longwall panel no.1 and all were successfully negotiated without any fall or
cavities. The periodic weighting interval was varying from 10m to 20m and the
average periodic weighting interval is 14.5m. The weighting zone was from 30th to
130th shield (about 175m length) out of total 146 nos shields in 250m face length.
The weighting zone was covering 70% of the total face length. During the periodic
weightings, about 40% shields were bleeding in the weighting zone. The weighting
was cleared after 4 to 6 shears of retreat.
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Mean Load Density (MLD T/m2): To monitor the efficacy of shields, the mean load
density (MLD, T/m2) was monitored in three zones namely Bottom, Mid, Top of the
longwall face.
Fig 19: MLD vs face progress
Observations: The following were observed from the analysis of MLD in the face
(Fig 19).







The MLD is more in the mid zone and then bottom zone and least recorded is
in top zone (TG side).
The MLD is more towards dip side or MG side compare to the rise or TG side
side may be due to effect of seam inclination or more depth towards the MG
side, where the vertical pressure is more.
The mid zone recorded maximum MLD because of most of the shield will
experience bleeding due to weighting. The maximum MLD recorded is 102
T/m2.
The shield support resistance after cut is 107 T/m2.
The mean load density in the mid zone is always less than the shield support
resistance indicated the shields are perfectly rated for the mine geo
conditions (Fig 16).
During weightings, the maximum MLD in the mid zone varies from 99 to 102
T/m2 corresponding pressure value is 424bar compare to yield pressure
450bar.
The maximum MLD in the bottom (MG) zone is 90 to 94 T/m2 and for the top
zone is 88 to 92 T/m2.
Overall observations from longwall retreat: From the weightings of longwall panel
no.1 the following were established.
 The main fall distance was 83m and the area of exposure 23205 sq.m.
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






During the main weighting, the Maximum MLD in the mid zone was recorded
101 T/m2.
The periodic fall interval is 14m. The maximum MLD recorded was 100 T/m2.
Every 3rd or 4th periodic weighting was severe due to failure of main roof and
upper main roof. The MLD during these weightings was recorded 101-102
T/m2.
The periodic fall interval was almost equals to the average thickness of main
roof above the No.1 seam.
The weighting zone was 30th shield to 130th shield covering 70% of total face
length.
The front abutment zone was confined to 25m ahead of the face.
During the weightings, the rate of convergence was about 36mm/day and
during non weightings the rate of convergence was 9mm/day within 25m from
the face when face progress was 4 to 5 m/day.
Subsidence monitoring: Subsidence pillars were constructed at 30m grid pattern to
study the subsidence over LWP No1. The LWP No1 was started on 15.10.2014 and
retreat was completed. OB dumps exist over the panel up to 1100m distance from
the face start line (from 0 to 500m distance upto 60m height and 500 to 1100m
distance to 45m height). The following were observed from the subsidence
monitoring:
 First subsidence was noticed after retreat of 350m to 400m in the month of
April-2014 when the depth is equal to face retreat.
 There was no subsidence due to barrier effect in first 150m from face start
line.
 The maximum subsidence recorded of about 1500mm on original ground and
1900mm over the OB dumps within the panel, which are more than the
predicted values of subsidence may be due to more number of clay bands
and the presence of water bearing strata in the over burden .
 The maximum subsidence point shifted for about 50m towards the dip side
from the panel center.
 The subsidence was active up to 350 to 370m behind the face.
 The maximum angle of draw is 130 towards dip side (MG side) and towards
rise side it is 60 when measured across the panel.
 Crack widths of about 5mm to 20mm were observed at the dip side of the
panel extend up to 100m from the panel edge. Maximum width of the cracks
observed near the panel edge and reduced further away from the panel edge
towards barrier side. However distinct cracks attributing to subsidence could
not be clearly seen on the rise of the panel.
Surface borehole extensometer: First time surface borehole extensometers were
installed for more than 350m depth, to study the caving behavior of the LWP No1
above No1 seam of ALP at 1130m, 1475m and 1700m locations from the longwall
installation face which were located at the middle of the face (Equal distance from
the Main gate and Tail gate). The installations were completed when the longwall
face was away from the location and not affected due to longwall extraction. Anchors
were located at different horizons from the surface to monitor the bed movements
17 | P a g e
with reference to longwall face extraction. During the initial stages, it was studied at
with two anchors at 1130m location but at 1700m location, up to surface movement
was studied by installation of six anchors located at 10m, 65m, 125m,230m,295m
and 345m above the face. The following were observed from the monitoring of
surface borehole extensometers.
 The bottom most anchor was installed 10m above the face (i.e 405m from the
surface).
 The anchor in the main roof was moved during the immediate periodic fall at
15m retreat from the face and anchor in the upper main roof was moved
during the 3rd periodic fall corresponding retreat from the location of about
40m.
 The movement of main roof was causing the periodic weightings in the face
and movement of main and upper main roof with the thickness of about 50 to
70m was causing the severe weightings in the face.
 After retreat of 50m from the location, the first subsidence of 101mm was
recorded along with the beds located at 295m and 345m above the face were
moved.
 The readings were active up to 320m behind the face and after that getting
stabilized, whereas the subsidence was active up to 350 to 370m behind the
face.
 The overlying strata up to surface was falling regularly and filling the goaf
completely.
Recommendations: The following are recommended for effective strata control in
wider and deep longwall panels.
1. Detailed geotechnical analysis of strata is required and suitability of the
technology shall be studied with the detailed modelling, before introduction of
the wider longwalls.
2. Meticulous planning for the design of panels, assessment of support capacity
basing on mine site geo-mining conditions and complete analysis of caving
behavior of the roof strata were required, to eliminate unexpected strata
problems during extraction.
3. Strata control Trigger Action Response Plans (TARPS) shall be prepared for
both development and retreat of longwall panel and implemented accordingly.
4. Regular strata control monitoring is required during the development of gate
roadways and regular auditing shall be done to ensure the stability of the
roadways and efficacy of bolting system.
5. High standards of roof bolting system shall be implemented during the
development of gate roadways with mechanized hydraulic bolting rigs.
6. In detailed monitoring of gate roadways, longwall face and chain pillars is
required during the retreat for successful extraction of longwall panel.
7. Secondary supporting shall be done with Resin anchored bulbed cable bolts
for longwall retreat and at wide installation faces.
8. Regular monitoring of shield leg pressures, weightings and subsidence shall
be done for ensuring complete caving of the roof strata.
18 | P a g e
Conclusions: Stability of the gate roadways during development and retreat is vital
for success of any wider and deeper longwalls and it can be achieved with proper
planning and implementation of standards. Major horizontal stress played a major
role in development of roadways especially weak roofs. Roadways shall de
developed in favorable direction to the major horizontal stress direction to avoid
strata control problems. Fast and slow set resin with high grade shear pin bolting
with pre tensioning will improve the strata conditions in weak roofs. Rigid wire mesh
eliminated the skin failures in the roof and improved the stiffness of the support
compare to linked wire mesh. Selection of correct horizon by making the strong
immediate layer improves the strata conditions. Auditing and TARPs helped to avoid
strata problems in roadways. Resin anchored bulbed cable bolting is a viable
solution for secondary support in high capacity longwall gate roadways and
installation faces to withstand for abutment loads and reduce the high convergence
rates. In TG2, the convergences were active up to 260m behind the face which was
equals to the width of the longwall. The convergences in TG2, overlying bed
movement of strata (data from Surface MPBX) and subsidence were behaving in
similar manner behind the face. From MLD monitoring data, it was observed that the
shield supports are adequately rated for geo-mining conditions of Adriyala Longwall
Project. At ALP, till date there was no delay in the production due to strata control
problems, indicates the roadways and the longwall face are within the control and
expecting the same in future longwalls by meticulous planning and execution.
Acknowledgment: The authors wish to express their sincere appreciation and
grateful thanks to the management of SCCL for their support and cooperation, for
permitting to present this paper and also permitting to use certain data for presenting
in this paper.
References:
1. Ajoy K.Ghose, 2008,”Longwall mining in INDIA-The next mile stone”,Journal
of mines metals and fuels,Nov-2008.
2. B. Ramesh Kumar, S Chandrasekhar and B Veera Reddy, “Need to think one
step ahead – High Capacity Longwalls in India, SCCL experience,” in
International Mining Conference-2015 at New Delhi, India.
3. B. Ramesh Kumar, S Chandrasekhar and B Veera Reddy, 2016,”Construction
and Operation of High Capacity Longwall Project – Adriyala Experience”, An
international conference on Recent advances in rock engineering, at
Bangalore16-18 November, 2016.
4. Russell Clive Frith, 2016, “Geotechnical Challenges and Achievements ToDate at the Adriyala Longwall Project (ALP)” Workshop on successful
introduction of high capacity longwall at Adriyala, at Hyderabad, India.
5. Russell Clive Frith, 2009,”ALTS 2009 - A Ten Year Journey”,Coal Operators'
Conference, 2009. Australia, pp: 37-53.
6. Dr. Russell Clive Frith, “technical reports on strata control” on ALP
7. Manoj Khanal, Deepak Adhikary, Rao Balusu,2012,”Assessment of Chock
Capacity and Strata Caving for a Longwall Mine”, Geotechnical and geological
engineering, April- 2012.
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