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“COMPARISION OF OPERATIONAL DIFFICULTIES
IN LONGWALL DIP RISE & STRIKE PANELS”
- A.Venkateshwer Reddy, Addl. Manager,
Project Planning DepartmentThe Singareni Collieries Company Limited
BACK DROP
• It is necessity to explore low capacity Longwall mining, where geological conditions permits to work 500m to 1000m length panels in SCCL to get bulk production as well as to reduce the cost of production.
BACK DROP
• The major challenges a head is, whether to follow principal stress direction while driving Gate roads or to plan according to the shape of property.
• Most of the future Longwall mine panels need to be laid in Dip Rise Direction, if Principal stress direction is taken into consideration.
EXPERIENCE
• Though, GDK-10A mine is being worked Strike & Dip rise Panels successfully, the gradient of Dip Rise Panels is 1 in 6 to 7. Where as in the proposed Longwall mines, Dip Rise Panels are around 1 in 4 gradient.
TRUNKS
• Formation & Maintenance of Trunk roadways is problem in a direction perpendicular to principal stresses.
• Trunk roadways have to maintain longer periods and needs high stability.
• Under increased stress condition on gate roads, needs additional supporting like resin bolting, cable bolting, roof stitching, arching etc.
GATE ROADS
• More stable when laid parallel to principal stress direction.
• Accumulation of Water in dip galleries, increased head of pumping in developing gate roads and insufficient quantity of water for dealing with high head pumps.
• Low Gate road progress per month, i.e., less than 100m• If twin or multiple entry system for gate road
development adopted in future, drivage is difficult in dip rise panels.
• Difficulty in Material Transport and handling on increased gate road gradients.
• Necessitates high capacity haulers /conveyor belts, including man riding if provided.
GATE ROADS
• Movement of free steered vehicles along gate roads is not feasible
on increased gradients.
• Only rail car man riding system for men transport along lengthy gate
roads is applicable. Chair lift system is not possible as frequent
shifting of return pulley while Longwall face under retreat.
• Switch train shifting is tedious and generally for every 100 m,
necessitates mono rail system for handling cables.
• Emulsion supplied to supports could not return to Power pack tank
through ring main system, leading poor quality of water emulsion
mixture and more consumption of emulsion oil.
• Increased Load on relay bars, advancing rams, face sprags of
powered roof supports.
• Ram capacity & plate size for face sprags of powered roof supports
need to be increased.
FACE
• Face spalling is more and directly falls between AFC, on spill plates & walkway
• Requires advancing chocks by adjacent control due to face spalling while lowering support.
• Leading to uneven wear of pans of AFC and flights overriding due to increased cross gradient of face.
• Proper cleaning is required for advancing AFC, even shearer provided with cowl.
• Shearer goaf side track shoe life reduces as more weight of shearer shifted due to cross gradient factor.
• Wear & tear of rack bars & spacers is high, as above.• Less load on shearer haulage due to reduced
longitudinal gradient.
FACE
• Increased risk to shearer operator &others working nearby due to face spalling.
• Subsidence is not uniform due to panel varies from shallow to high depth- possibility of increased breathing from surface.
• Whenever heating or fire problem arises, could not easily dealt by method of inertisation and also not possible to drown the workings with water as an ultimate option.
• For outby transport of coal in gate road need to provide two or more gate belt drive heads due to increased lift.
FACE
• Shearer sump low due to increased cross face gradient. • Face and gate roads are dry if drainage planned is
towards the goaf.• Less humid and comfortable ventilation conditions.• Crushing of barrier pillar is minimized compared to strike
panels.• In AFC, Gravity component is eliminated for coal
transport.• AFC motor capacity to be increased as gravity does not
support. (Requires high initial torque).• No slushy condition at BSL.
FACE
• Face strata control problems are less.
• Periodic weighting interval is less
• Cavities formation in face is less due to front abutment
pressure is less and more load is shifted to goaf side.
• Salvaging is safe and easy due to load on PRS is less.
• Face progress is less compared to strike panels.
• Property loss is more because of shape of property
favors strike panels.
• Opined to work one dip rise short length panel in steep
seam on experimental basis.
SUMMARY
• As far as possible, strike panels are more
convenient in operational aspect. Gate roads
need to be laid oblique to Principal stress
direction and increasing support density to
counter the strata control problems.
• Wherever strike panels are not feasible
keeping in view of shape of deposit and
principal stress, it is obvious to work dip rise
panels by overcoming the operational
difficulties.
• It is suggested to work Strike panels,
instead of Dip Rise Panels in view of the
difficulties forecasted in dip rise panels
with 1 in 4 gradient.
CONCLUSION
COMPARISON OF DIP-RISE LONGWALL PANELS WITH STRIKE LONGWALL PANELS
S.No Parameters Dip Rise Panels Strike Panels
1 Drivage of Single or multiple Gate roads
Moderate Difficult ✕ Easy ✔
2 Gate road progress Less ✕ More ✔
3 Gate road condition Dry ✔ Slushy ✕
4 Material and men Transport in Gate roads
Risky ✕ Less Risky ✔
5 Laying & Dismantling of gate belts
Difficult ✕ Easy ✔
6 Number of Belts required in Main gate
Two or More depends upon lift
✕ Single ✔
7 Switch train Shifting Tedious & cables handling is difficult
Requires one time shifting for every 100m or more
✕ Easy & shifting can be done daily
✔
8 Water DrainageDuring DevelopmentDuring extraction
Requires pumpingGood
✕✔
Does not require pumpingNot Good
✔✕
9 Ventilation Comfortable due to dry condition
✔ Less Comfortable due to humid condition
✕
10 Face Spalling More ✕ Less ✔
11 Main Weighting Span Less ✔ More ✕
12 Periodic weighting interval
Similar ✔ Similar ✔
13 Periodic weighting intensity
Less ✔ More ✕
14 Strata Control Problems Less ✔ Moderate ✕
15 Emulsion requirement for supports
More ✕ Less ✔
16 Safety to workmen Less ✕ Moderate ✔
17 Load on Shearer haulage
Less ✔ More ✕
18 Wear & tear of face equipment (AFC & Shearer Parts)
More ✕ Less ✔
19 Face Equipment Creep problem & Control
Less ✔ More & Difficult ✕
20 Sequence of Cutting Limited to Uni-directional only
✕ Uni or Bi-directional ✔
21 Sump to each Cut Less ✕ More ✔
22 Production Less ✕ Moderate ✔
23 Coal Transport in AFC Gravity does not support ✕ Gravity supports ✔
24 AFC Motor Starting Torque Requirement
High ✕ Moderate ✔
25 Salvaging & installation Easy ✔ Moderate Difficult ✕
26 Dealing of Heating or fire Problem
Difficult & Unsafe ✕ Moderate Difficult & safe ✔
27 Subsidence over goaf Non-uniform ✕ More or less Uniform ✔
28 Effect of Principal stress on Trunks
More because aligned perpendicular
✕ Less because aligned parallel ✔
29 Effect of Principal stress on gate roads
Less because aligned parallel
✔ More because aligned perpendicular
✕
30 Alternative to lower effect of Principal stress
Trunks need to be aligned oblique to stress direction
✔ Gate roads need to aligned oblique to stress direction
✔
1119
1911