Effect of longwall workings on the stability of overburden dumps

Abstract

Extraction of coal is done in both opencast and underground methods. Opencast mining generates a huge amount of overburden while excavating the coal. Managing the overburden material, deposited as dumps at considerable heights to minimize ground coverage, is crucial in opencast mines, but it poses risks such as potential failures. Such failures can stop the mining activities, endanger personnel safety, and damage equipment. At times, limitations in space, the placement of overburden dumps over underground excavations, posing stability challenges due to pre-existing stresses from activities below the surface. This paper explores the stability prediction of overburden dumps above longwall workings, using Rocscience RS2 v19.2, a two-dimensional finite element analysis software. Strength Reduction Technique determines the factor of safety (FOS), revealing that the presence of underground longwall excavation induces a vertical deformation of 56.4mm for the critical strength reduction factor of 1.12, emphasizing the impact on overburden dump stability. © 2024 The Author(s).