Abstract: Deep rock is characterised by high stress and large deformation in underground engineering. It is of great significance to investigate its mechanical properties by conducting the triaxial tests under high confining pressure and considering a residual strength. The distinct element method (DEM) is an essential numerical method for analysing the mechanical properties of rock. However, there have been many challenges in quantitatively simulating the rock by DEM in the triaxial tests. The reason is that it is challenging to quantitatively reproduce the complete stress-strain curves of rock using DEM. By considering the residual strength of rock, the triaxial compression tests on deep sandstone were quantitatively simulated by DEM using the improved three-dimensional (3D) bond model incorporating rolling and twisting resistance. The results show that this study successfully achieves the quantitative reproducing of the complete stress-strain curves. The large peak/residual internal friction angle and nonlinear strength envelope of rock are obtained as well. Meanwhile, this study overcomes three prominent challenges of the classic bonded-particle model (BPM). The relationships among the peak/residual internal friction angle, cohesion and microscopic parameters of DEM are discussed through a large number of simulations. At the same time, the high computational efficiency is proved using the improved model, which can satisfactorily meet the requirements of the 3D simulation for conventional laboratory tests.

Key words: deep rock, residual strength, triaxial test, quantitative simulation, distinct element method, parameter analysis