Caveability assessment and support planning for adequacy of the existing supports under caved goaf of overlying seam - a case study

In India the experience of longwall working is not encouraging. This is mainly attributed due to difficult caving strata and poor support performance at the face. Severe and intensive weighting is experienced at the face due to mismatch/underrating of the support capacity at a locale causing partial or complete failure of the longwall mining system. This can be avoided by detail technical study by caveability assessment of the overlying roof rocks at a locale prior to installation of a longwall face. Caveability assessment helps in selecting a sustainable support capacity for a range of height of extraction. An available support system can also be utilized effectively at a locale for selective height of extraction. In this paper, support resistance requirement has been estimated prior to extraction at AW-2 longwall panel for two boreholes at 150m and 650m over the panel for different height of extraction using CMRI approach based on caving index of roof rock beds. The study was undertaken as a part of a consultancy assignment fromECL management. It was recommended to use the Ex-Satgram support for extraction of 2.2-2.4m of RVIIA seam at AW-2 longwall panel which was lying 45m below the caved goaf of W-2 panel in RVII seam