System reliability assessment for section coal pillar with multiple failure modes

Coal Pillars are important structural elements in underground mining Unstable pillars can result in collapse of roof and walls and even coal burst; hence its reliability analysis is of great importance. This paper presents a novel probabilistic framework to assess system reliability of section pillar. The variation of coal mass parameters, such as UCS, friction angle, cohesion and Young's modulus, are considered. Two different failure modes, with respect to pillar stress and strain, are investigated to obtain reliability indices using FLAC(3D), Stochastic response surface (SRSM) and First-order reliability method (FORM), then Bimodal bound and Linearization methods are adopted to compute system failure probability. Finally, coal mass parameters from a typical coal mine are employed and results suggest that both stress and strain limit states could have significant influence on the system reliability. The approach proposed in this paper could be a useful tool on the risk management of underground pillar.