Estimation of spalling strength of sandstone under different pre-confining pressure by experiment and numerical simulation

Abstract

Spalling failure is a common underground engineering disaster, particularly in deep environments with high geo-stress and strong stress disturbances. Therefore, the further investigation of the spalling behaviour of rock under different pre-confining pressures is of considerable importance. In the presented work, a modified split Hopkinson pressure bar (SHPB) system is modified with a pre-confining loading device that can apply pre-static loads to Φ50 mm × 300 mm specimens. The system is employed to study the spalling characteristics of rock specimens subjected to full pre-confining pressure. Spalling tests of Φ50 mm × 300 mm rock specimens under different pre-confining pressures were conducted. The experimental results indicated that spalling failure was influenced by pre-confining pressure. Furthermore, numerical simulations with the same loading conditions as the experiments were conducted using the finite element software, LS-DYNA, and the spalling strengths of the rock specimens under different pre-confining pressures were obtained based on the improved stress wave analysis method. The results indicated that the stress wave analysis method in view of numerical simulation can effectively be used for calculating the spalling strength of rock and rock-like material under pre-confining pressure. The spalling strength of the rock specimens increased first and then decreased as the pre-confining pressure increased.