Numerical analysis of a large landslide induced by coal mining subsidence

摘要

Mining induced subsidence is one of the challenging problems in geotechnical engineering. The surface topography of the ground over mining excavations plays a key role in the mechanism of subsidence. When a mining operation is performed beneath mountainous or hilly terrain, it may trigger landslides. This study, therefore, aims to analyse the impacts of underground mining on the stability of slopes by using numerical modelling. A coal mining induced landslide at Nattai North, Australia, is investigated as a typical case study. In this area, mining operations beneath the Sydney Basin escarpments initiated the largest contemporary landslide and mass movement known in Australia (Cunningham, 1988). Discontinuous numerical modelling is employed to analyse the mechanisms of the ground movements leading to this landslide. The role of geological and geotechnical factors, such as rock mass characteristics, bedding, and joints, are discussed through the numerical modelling. The outcomes of the analyses reveal that mining induced stresses lead to the shear and compressive failure of weak strata at the escarpment base, particularly around its toe. The failure of the base materials as well as the caving of the overlaying bedded rocks into the extracted panel, facilitated the detachment of the massive sandstone. This rock column ahead of the escarpment, was overlaying the weak strata. The numerical results also indicate that the aforementioned rock column remained almost unaffected during mining. However, the failure of the weak strata at the toe of the escarpment initiated the simultaneous forward sliding and toppling of the rock column. This mode of failure which is known as ski jump type of failure, was previously observed and eXplained by Pelts et al. (1987). (C) 2016 Elsevier B.V. All rights reserved.