Most of the coalfields of India consists multi-seam mining conditions, where a majority of the coal seams have 9m or less inter-burden parting thickness called contiguous seams. Many of these contiguous seams have weak and laminated parting. Underground extraction of contiguous seams and sections especially, by a room and pillar system is a challenge due to the problems of pillar load transfer and instability of the thin, stratified and weak parting. A series of laboratory investigations are conducted by numerical modelling using three dimensional finite difference code FLAC3D to visualize the behaviour of the weak and stratified parting under varying conditions of underground development of the contiguous seams/sections. The study also involved techniques and procedures for strengthening of weak and stratified parting between the contiguous coal seams/sections by reinforcement for a room and pillar development. On the basis of this study a better sequence of extraction is established for development of contiguous seams and sections. This paper presents the simulation results of parametric study as well as actual site conditions by numerical simulation in the laboratory and a methodology for strengthening of parting for development of contiguous seams/sections under weak and laminated inter-burden strata.
Most of Indian coalfields inherit a number of difficult geomining conditions; multi-seam mining condition is one of them. Considerably large amount of coal reserve in India is present in form of contiguous coal seams/sections, which make underground mining challenging. To meet the demand of coal, a number of thick seams of the country is also developed or need to be developed on pillars in different horizons, which also create a case of contiguity. According to Indian Coal Mines Regulations, 1957, contiguous seams/sections are those which lie within 9m of each other . The challenge increases manifold if the inter-burden parting of contiguous seams/sections is thin, weak and laminated. Many of these contiguous seams/sections have weak and laminated parting making these difficult for development of both the seams by the most prevailing room and pillar system of development, popularly called „bord and pillar" method in India. Working of these seams/sections warrants special attention about the competency of the parting since it serves the dual role of being the floor of the upper seam/section and the roof of the lower seam/section workings. The pillar load transfer phenomenon, up to some extent, can be controlled through superimposed development of the two close seams/sections, but the presence of highly bedded weak strata between the two close seams/sections becomes a bottleneck for development of both the seams/sections. A significant portion of our coal reserve under contiguity condition could not be developed or extracted due to presence of weak parting, which requires in depth study to find out a method for strengthening of parting during development. It also needs further study with an objective to reinforce the parting to avoid its premature failure during depillaring. Initial study through literature review suggested  that reinforcement of weak and laminated parting is a favourable option.