Knowledge of the uniaxial compression strength of rock mass is crucial for evaluating the stability of rock pillar in the underground engineering. The inherent and spatial variabilities of rock mass properties are generally ignored in the classical stability evaluation of rock pillars. In this study, probabilistic analysis of uniaxial compression strength of rock pillar was carried out to investigate the compressive responses of spatially variable rock pillars with a 3D random field. The 3D random field of rock mass properties was generated by the Cholesky decomposition method, which was implemented into the FLAC3D using the Fish code. Influence of spatial variability of rock mass properties on uniaxial compression strength and Young's modulus was investigated by Hoek-Brown criterion with Latin hypercube sampling (LHS). The results indicated that the spatial variability of rock mass properties has a significant influence on the uniaxial compression strength and Young's modulus of rock pillar. The vertical scale of fluctuation has a greater effect on the mean value and standard deviation of the uniaxial compression strength and Young's modulus of rock pillar than the horizontal scale of fluctuation.
Due to the differences in mineral composition, sedimentary conditions, stress history and other geological processes, the spatial variability of mechanical properties of rock mass is generally considerable (Chen et al.2019). The influence of spatial variability on the strength of soils has been investigated by many researchers (Ching and Phoon 2013; Ching et al.2016; Tabarroki and Ching 2019; Chenari et al.2019). However, there is almost no reference about the strength of rock mass considering the 3D spatial variability (Griffiths et al.2002; Renani et al.2019). In underground openings, rock pillars are generally used to support the roof, which are always under uniaxial compression state. Pillar failures are apt to result in serious disasters. The conventional deterministic method commonly adopts the mechanical tests in laboratory or field instrumentation to evaluate the stability of rock pillar, while the inherent uncertainties and the spatial variability of rock mass have been generally ignored, intentionally or unintentionally. Therefore, it is essential to investigate the influence of spatial variability on the uniaxial compressive strength of rock pillars.