Assessment of Rock Load Height at The Goaf Edge During Depillaring with Stowing: A Numerical Modelling Study

Abstract

Underground coal mining in India is increasingly directed toward maximizing coal recovery from standing pillars, many of which lie beneath critical surface features such as railways, water bodies and residential areas. Depillaring with stowing is widely adopted to control strata movement and limit surface subsidence, thereby protecting these surface structures. However, support design at the goaf edge during depillaring with stowing is often based on guide-lines originally developed for caving systems of goaf manage-ment. A proper understanding of roof-pillar interaction at the goaf edge during depillaring with stowing is essential for optimizing support resistance and achieving safe, efficient, and economical coal extraction. This study presents a systematic three-dimen-sional numerical modelling approach to estimate the Rock Load Height (RLH) at the goaf edge of a stowing panel. A parametric analysis was performed using the Sheorey failure criterion, vary-ing the Rock Mass Rating between 30 and 65 and the gallery width between 3 m and 5 m. The results indicate that sand stowing pro-vides significant confinement to the ribs, effectively reducing the side spalling commonly observed in caving panels. The study fur-ther shows that goaf-edge support requirements can be optimized through appropriate modification of the support system design.