Development of Safe Cut‐Out Distance Framework for Continuous Miner Operations in Indian Underground Coal Mines: A Numerical Simulation and Field Studies

ABSTRACT The continuous miner (CM)‐based coal extraction was introduced two decades ago in Indian coalfields. Safe cut‐out distance (COD), represents the maximum safe and stable span of a fixed‐width gallery excavated in a single pass using CM. The amount of coal that can be cut at once without support defines the successful implementation of CM. The existing guidelines exhibit considerable variation under similar conditions, making it challenging to determine a safe COD. In this research, a simulation study is carried out for 20 selected panels of different coalfields in India, considering strain‐softening material properties for the immediate roof to accurately capture the geo‐mechanical response. The simulation study found that Rock Mass Rating (RMR), Young's modulus, gallery width, and depth of cover are the most influential parameters in determining safe COD. Safe COD is defined considering a maximum displacement of 5 mm before the installation of roof bolts in the numerical modelling. Multivariate regression analysis is carried out on the basis of the measured safe COD in the models under different conditions, and a formulation is developed with an R 2 value of 0.86. The developed formulation is validated in the field through strata monitoring observation and found to predict the safe COD consistently compared to the other available design guidelines. However, this formulation applies only in the absence of weak geological disturbances and is unsuitable for areas affected by such conditions. This newly developed design guideline increase productivity and reduce the cost and time involved in designing the COD in the field.