Longwall mining (Multisling mining - Horizontal slicing) NIT ROURKELA
- 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