critical review of extraction of strike longwalls versus dip rise longwall panels in SCCL AP india, operational and planning parametres to be considered for working the same

1. Critical Review of Working Strike
Longwalls Versus Dip-Rise
Longwalls
U Siva Sankar
Sr. Under Manager,
Email;uss_7@yahoo.com
ulimella@gmail.com
Group 2 Group 1 Group 3
Working layout of GDK -10A Incline
1

2. Orientation of Panels
Principal Stress Direction of ADRIYALA & GDK-10A
is NNE 240
Panel With True North
Strike Panels N 110 to 260 W
(Dip-Rise Face)
Dip Rise Panels N 670 E
(Strike Face)
At Adriyala, M/S MESY India conducted 17 successful
hydrofrac tests for the determination of a stress-depth
profile for the depth range between 77 m and 522 m.
For all of the 17 hydrofrac tests the orientation of the
induced fractures was determined by impression packer
tests.
The mean azimuth of the vertical fractures was
determined as N (24 ± 14) degrees (NNE)
Mean stress-depth relations for the minor and major
horizontal stresses and verical stress
Major Horizontal stress vertical Stress varies from 1 to 1.2
times vertical stress at 300m to 500m depth
2

3. Orientation of Panels
Gradient of Gate Roads and Face
Panel Longwall Face Gate Roads
Strike Panels 1 in 6 to 1 in 6.2 1 in 20 to 1 in 25
(Dip-Rise Face)
Dip Rise Panels 1 in 50 to 1 in 60 1 in 6 to 1 in 7
(Strike Face)
3

4. Support System
• MECO- 4x800 tonnes IFS powered Roof
Supports are being used.
• Face sprags are being used in dip – rise
panels
Creep Control
Strike Panels Dip –rise Panels
(Dip –Rise faces) (Strike Faces)
Staggering MG is Kept 10 to 15 MG is Kept ± 2m ( < 10
m (40 to 60 swing ) in swing )of TG
advance of TG
Monitoring Regular Monitoring is Even with negligible
Required monitoring, no major
movement of face
machinery was observed.
4

5. Weighting Details
Strike Panels Dip –rise Panels
(Dip –Rise faces) (Strike Faces)
Main 72.00 m (Panel # 55.10 m (Panel # 3B) &
Weighting 3A) 53.00 m (Panel # 3C)
Periodic Regular at an Regular at an interval of
Weighting interval of 7 to 25 m, 5 to 28 m, with an
with an average average interval of 17 m.
interval of 16 m.
Intensity More (readings) Reduced
(C30 to C80 is (C30 to C75 is Supports
Supports Yielding Yielding Zone)
Zone)
Face, Roof and Gate Roads Stability
• Slabbing in face is more in Strike face compared to dip-
rise face and it was 2m ahead of tip of canopy during
periodic weightings. (Direction of cleavage planes plays
role)
• Cavities were also frequent at the time of weightings in
strike faces compared to dip – rise faces
• Cavities & Slabbing in Face was reduced & Safety was
also improved with the introduction of Face sprags in
strike faces.
• In strike Panels guttering was observed in gate roads.
5

6. Horizontal stress - Longwalls
• Horizontal stress can not pass through
gob area or broken or collapsed roof;
therefore zones of stress relief and stress
concentration are created
• Their location depends on panel
orientation, direction of retreat and
sequence of extraction
Gate Road Stability with respect to horizontal stress
(After Mark)
6

7. From the study with AHSM (Analysis of Horizontal
Stress Measurement) NIOSH software
Group 1 Panels as the panels are falling stress
concentration zone
while Group 2 strike panels are falling in stress
relief zone and
Group 3 Dip rise panels are falling under stress
concentration zone
Drainage
Strike Panels Dip –rise Panels
(Dip –Rise faces) (Strike Faces)
Make of 450 GPM – Normal Initially observed but after
Water period & 650 GPM – main fall no seepage.
after Periodic
Weighting
Drainage Goaf to MG out by Goaf to dip most Sump
through dip side level
gallery
Face is Dry and Coal Quality not affected in Strike faces compared
to Dip – Rise faces
7

8. Modifications - Strike faces
• AFC Motor capacity was increased from
2x150 kW to 2x250 kW as gravity does not
support material transport
• In Main gate Three 2x150 kW Gate belt
gear heads were installed for coal
transport due to higher lift (≈160 m)
Other Observations
• Stoppage of longwall face at the time of
Gate belt Gear head dismantling and Gate
belt jointing works( one day)
• Switch train shifting & cables handling is
tedious and requires special care. (Cables
of 100m additional length required for one
time shifting for same length)
8

9. COMPARISON OF DIP-RISE LONGWALL PANELS WITH STRIKE LONGWALL PANELS
Parameters Dip Rise Panels Strike Panels
Drivage of Single or multiple Moderate Difficult ✕ Easy ✔
Gate roads
Gate road progress Less ✕ More ✔
Gate road condition Dry ✔ Slushy ✕
Material and men Transport Risky ✕ Less Risky ✔
in Gate roads
Laying & Dismantling of Difficult ✕ Easy ✔
gate belts
Number of Belts required in Two or More depends upon lift ✕ Single ✔
Main gate
Switch train Shifting Tedious & cables handling is ✕ Easy & shifting can be done ✔
difficult daily
Requires one time shifting for
every 100m or more
Water Drainage Requires pumping ✕ Does not require pumping ✔
•During Development Good ✔ Not Good ✕
•During extraction
Ventilation Comfortable due to dry ✔ Less Comfortable due to humid ✕
condition condition
Face Spalling More ✕ Less ✔
COMPARISON OF DIP-RISE LONGWALL PANELS WITH STRIKE LONGWALL PANELS
S. Parameters Dip Rise Panels Strike Panels
N
o
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 More ✕ Less ✔
supports
16 Safety to workmen Less ✕ Moderate ✔
17 Load on Shearer haulage Less ✔ More ✕
18 Wear & tear of face More ✕ Less ✔
equipment (AFC & Shearer
Parts)
19 Face Equipment Creep Less ✔ More & Difficult ✕
problem & Control
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 ✔
9

10. COMPARISON OF DIP-RISE LONGWALL PANELS WITH STRIKE LONGWALL PANELS
S. Parameters Dip Rise Panels Strike Panels
N
o
24 AFC Motor Starting Torque High ✕ Moderate ✔
Requirement
25 Salvaging & installation Easy ✔ Moderate Difficult ✕
26 Dealing of Heating or fire Difficult & Unsafe ✕ Moderate Difficult & safe ✔
Problem
27 Subsidence over goaf Non-uniform ✕ More or less Uniform ✔
28 Effect of Principal stress on More because aligned ✕ Less because aligned parallel ✔
Trunks perpendicular
29 Effect of Principal stress on Less because aligned parallel ✔ More because aligned ✕
gate roads perpendicular
30 Alternative to lower effect Trunks need to be aligned ✔ Gate roads need to aligned ✔
of Principal stress oblique to stress direction oblique to stress direction
Favour 11 Favour 19
Un-favour 19 Un-favour 11
Production Summary
Panel length Face length
Sl. No. Panel No. No. of chocks Total Production (T) Prod/day (T)
(m) (m)
1 1 980 150 101 764,148 2330
2 2 990 150 101 756,663 2433
3 3 1024 150 101 761,927 2426
4 10 850 140 94 551,577 2113
5 10A 555 158 111 434,416 1285
6 11 900 110 78 358,791 880
7 7 955 118 80 532,620 1091
8 12 720 93.5 66 361,126 1852
9 8 990 115/135 77/90 619,384 1701
10 3A 1014 160 108 921,335 2090
11
* 3B 1030 150 101 810,725 1814
12
* 3C 900 150 101 1795 tonnes per day
* Dip – Rise Panels (Strike faces)
10