Longwall mining (Multisling mining - Horizontal slicing) . longwall development in multiple seam ,slicing methods , extraction processes

1. MULTI SLICING – HORIZONTAL SLICING
PRESENTED BY INDRAJEET KUMAR
ROLL NO 117MN0654

2. CONTENTS
1. What is longwall mining?
2. Longwall in India
3. Longwall layout
4. Longwall mining method
5. Multislicing in thick seam
6. Horizontal slicing
7. References

3. What is longwall mining ?
1. Longwall mining is a form of underground coal
mining where a long wall of coal is mined in a
single slice (typically 0.6m – 1.0m thick)
2. The longwall panel is being is typically 3-4 km
long and 250 -400 m wide
Source: mining.com

4. LONGWALL IN INDIA
1. First mechanized powered support longwall
caving face was introduced in August 1978 at
Moonidih, CIL.
2. First Longwall face introduced in GDK.7
.Incline in September 1983 in SCCL.
3. In India currently only about 2% of U/g coal
production comes from longwall mining.

5. Longwall mining Layout
Source: scieio .org.za

6. Lonwall shearer
Powered roof support
Armoured face conveyor

7. Longwall faces in India
MOONIDIH ,JHARIA (BCCL) GDK 7 INCLINE (SCCL)
Seam - XVII Top seam Seam no III
Thickness - 1.75 Thickness - 10m
Gradient - 1 in 7 Gradient - 1 in 7
Height of extraction - 1.75 m Height of extraction - 3 m
Shearer capacity - 150kW Shearer capacity - 375kW
Goaf control - Caving Goaf control - Caving
Average production - 600 t.p.d Average production - 1163 t.p.d

8. Longwall mining method
Single pass
1.Longwall Advancing
2.Longwall Retreating
 We cannot extract thickness more than 4.8 m so
we go for MULTISLICING -
1. Horizontal slicing
2. Inclined slicing
3. Diagonal slicing
4. Cross slicing

9. Longwall Advancing
 It involves the extraction of panel of coal to be worked
by advancing the face forward on a wide front leaving
behind the roadways.

10. Longwall Retreating
1. In case of longwall retreating the face is
retreated on the roadways driven before
opening out the face and as the face is
allowed to cave in or it is filled and gate
roadway is lost in the goaf.
2. In India longwall
retreating is practiced.

11. Multislicing in thick seam
 Invariably thick seams are mined in multi slices.
 Bord and pillar is not used because this method does
not provide efficient strata control, results in heavy
loss of coal.
 Multislicing with longwall method is used for thick
and steep seams.
 Slices may be taken in both ascending or descending
order or in mixed order.

12. Slicing method

13. Horizontal slicing
1. Horizontal slicing is applicable to mining thick
seams ( more than 15 m thick )
2. It can be done both in ascending order or
descending order.
3. Filling of the goaf may be done by stowing or
caving.
4. To access the seam should be done by roads
driven in the footwall and cross cuts from the
footwall to the seam.

14. Horizontal slicing in ascending
order with stowing
1. The face is opened with a central gallery driven
through the seam connecting the drifts.
2. Normally eight longwall faces ; 4 on footwall side ,4
on the hanging wall side are opened and advanced
on the strike.
3. Coal is solid blasted on chain conveyor .
4. As face advanced ,goaf is stowed pneumatically.
5. The first slice is extracted upto 3m and stowed
,then the second slice was started over it.

16. Example in India
1. In Jharia coalfield ,IX & X seam combined was
opened up on horizon mining system and was
worked by horizontal slicing in ascending with
hydraulic sand stowing ( 16-22 m thick)

17. In descending order
1. It is done with artificial supports and with caving or stowing.
2. The face is opened up across the seam with a central gallery
driven on the strike.
3. Generally it is done with caving while advancing.
4. When face advances 60 m the top gallery is dug in two
stages of 1.5m each so that the floor is lowered by 3m.
5. The next slice was extracted below the artificial roof along
the floor of the previous slices, similarly the process
continues for further slices in descending order.
6. Coal is delivered on to the central gate belt by individual face
conveyors.
7. Thick and steeply seams are worked with this method , eg in
China.

19. References
1. SINGH, R.D (1997)“ Principles and Practices of Coal Mining” Ch 7
:Longwall mining PP 206 -214 , Ch 8: Thick seam mining PP 262 -
267
2. https://www.slideshare.net/venkoos/longwall-mining
3. Longwall machineries images ; okorder.com
;landsat.gsfc.nasa.gov