Quantifying strength and permeability of fractured rock mass using 3D bonded block numerical model

Abstract

In this research, a 3D bonded block model (BBM) is applied to numerically quantify the strength and permeability of fractured rock mass. The reliability of the BBM is initially verified through comparisons between conceptual models and theoretical and laboratory results. A series of rock mass models incorporating complex fracture networks is then constructed, and the strengths are quantified accordingly. The rock mass is weakened when low fracture stiffness and friction angle are assigned, and steep fractures are simulated. In both cases the low strength is attributed to the decreasing frictional resistance of the initial fractures. The rock mass is further weakened when more persistent fractures are simulated, in which the weakening effects of the fractures are amplified. The numerical models are compared with the widely used Hoek-Brown strength criterion. The strengths resulting from the two methods converge only when steep and less persistent fractures are simulated. Numerical simulations also suggest that in general, the permeability is positively related to the strength for rock masses that are impermeable in the pre-peak loading stage. In such cases additional flow paths are formed and attributed to failed rock bridges. The research works provide new options to quantify the strength and permeability of fractured rock mass, and offer opportunities to examine relations between these parameters.