Numerical Modeling Study of the Geo-mechanical Response of Strata in Longwall Operations with Particular Reference to Indian Geo-mining Conditions

Abstract

India has been seeking technology for mass production of coal below ground. Longwall technology was accepted as one of the options a few decades ago. Unfortunately, it failed to meet the expected benchmark for success. This shortfall was deciphered and attributed to the inadequate understanding of cavability, leading to a mismatch in support performances. Hence, the present study attempted to bridge the gap in understanding of the strata behavior in longwall workings for the Indian geological formations. Four longwall panels representative of the major Indian coalfields were selected for the investigation. An effort was made to supplement the design-based knowledge of longwall workings, under different geo-mining and strata conditions. The stress redistribution was observed with the progressive mining along with the model and field-observed mechanism of strata failure, caving, and support loading. The effect of mining activities on the failure and deformation characteristics of the strata was studied using Finite Difference software FLAC3D. It was found that the geo-mechanical properties of the overlying strata and the depth of mining were the most influential factors in controlling the behavior of the strata. At shallow depth, mechanical strength and the thickness of the overlying strata were identified as the main controlling parameters for most of the ground control events. However, at greater depths, face instability appeared to be the major contributor to these events. It is inferred that the proposed numerical modeling approach could be effectively utilized for evaluation of the stress redistribution, mechanism of failure, quantification of caving span, face convergence, and support loading for longwall panels in Indian geo-mining conditions.