Numerical modeling of time-dependent spalling of rock pillars

Abstract

Time-dependent deformation of brittle rock pillars is investigated using laboratory-scale pillar models using the grain-based time-to-failure model (GBM-TtoF). First, time-dependent deformations of rock pillars are analyzed and the results are compared qualitatively with field observations. Second, the influence of the boundary profile of pillar walls on time-dependent strength and deformation of rock pillars is investigated. Two factors, pillar shape and loading ratio, which influence the time-dependent strength and deformation of rock pillars, are studied by conducting a series of creep simulations using four pillar models with width to height ratios of W/H = 0.5, 1.0, 1.5 and 2.0. Finally, long-term strengths and deformation features of slender and squat pillars are analyzed. It is found that time-dependent strengths and deformation of rock pillars can be simulated using the GBM-TtoF creep model properly. Gradual spalling on the pillar walls can be captured using pillar models with rough boundary profiles. Creep deformations of slender and squat pillars could be quite different. Slender pillars are more likely to fail as time passes but squat pillars can tolerate more spalling on the walls without losing their stability. It is demonstrated that the GBM-TtoF creep model can simulate time-dependent strength and deformation of hard rock pillars well under creep loading conditions.