A.V.Reddy

“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