Mechanical properties and failure modes of rock samples with grout-infilled flaws: A particle mechanics modeling

Natural fractures are commonly infilled by the infilling materials, such as sheared-off or broken rock fragments and clay. Grouting has been widely used to improve the wellbore stability in oil or shale gas reservoirs and reduce the permeability of fractured rocks in tunnel vicinity, and thus rock fractures can also be manually infilled by grout. Although a large number of studies focused on the strength and failure behavior of rock samples with open flaws, the research on the mechanical properties and failure modes of rock specimens with infilled flaws is rather limited. In order to understand the effects of fillings on mechanical properties and crack propagation behavior of pre-flawed rocks, a large number of numerical uniaxial compression tests have been conducted for rock samples with single or double flaws which were open or infilled, using a particle mechanics method. The results showed that infillings play a significant role in improving the mechanical properties of pre-flawed rock samples, especially when the inclination angles of flaws are less than 45°. The infillings mainly play a role in transferring stress and reducing stress concentration at the flaw tip and bridge regions and thus infillings can change the crack initiation position, propagation direction and coalescence pattern in rock samples with infilled flaws. The effects of micro-parameters of infillings on the mechanical properties and behavior of rock samples with single flaws were also studied through sensitivity analysis.