Study of the size effect of rock mass with different random joint dip angles under direct shear based on the SRM method

Abstract

[Objective] Aiming at revealing the patterns of influence that random joints within different dip angle intervals have on the failure characteristics, shear strength, and size effect of the shear modulus of rock masses, [Methods] the SRM technology in PFC^2D discrete element software is used combined with fractal theory and the Monte Carlo method, and numerical simulation of direct shear tests is conducted on rock-like materials of various sizes with embedded random joints.[Results] The result indicate that:(1) The shear strength of the rock body shows “S”-type nonlinear characteristics with the increase of the inclination angle of embedded random joints, and the minimum value mostly occurs in the interval of 15°~30°, and the maximum value is in the interval of 60°~75°.(2) Different sizes of embedded random joints have similar effects on the damage of the rock mass by the change of inclination intervals. The low inclination interval shows obvious dominant and subdominant damage surfaces, and as the inclination interval increases, the stress concentration is shifted to the middle of the joints, and the dominance of the two dominant damage surfaces is switched.(3) The variation of random joint dip intervals significantly affects the size effects of rock shear strength and shear modulus, and the effect on the size effect of rock shear strength is greater than the effect on the size effect of shear modulus.[Conclusion] The study investigates the impact of variations in the embedded random joint dip angle intervals on the shear strength and failure characteristics of jointed rock masses under the same size conditions, as well as the influence of variations in the embedded random joint dip angle intervals on the shear strength and the size effect of the shear modulus of jointed rock masses under different size conditions. It provides significant reference value for the prediction of rock mechanical properties and their engineering applications.

Keywords

SRM method / PFC(Particle Flow Code) / random joints / direct shear test / size effect / shear strength / mechanical property