Effect of weak-filled layer properties on the mechanical response, crack evolution and failure characteristics of jointed rock

Weak-filled joint (WFJ) strongly influence the mechanical and fracture properties of the rock mass. Uniaxial compression tests were conducted on rock-like specimens containing weak-filled layer with a fixed inclination angle(45°) but different joint roughness coefficient (JRC). The results indicated that increasing JRC led to an initial rise and subsequent decline in peak stress (), a steady increase in failure strain (), and a transition in fracture mode from hard-weak interface sliding failure to mixed matrix tensile-shear failure. Based on the experimental results, a three-dimensional weak-filled jointed rock (WFJR) numerical model was developed using ANSYS/LS-DYNA to investigate the effects of JRC, thickness (T) and strength of WFJ on the mechanical response and fracture evolution. The increasing JRC promotes a transition in fracture mode from interface sliding to matrix splitting, and the greater T requiring small JRC required for the shift and inducing more extensive crack propagation. For WFJ rock with low strength, the failure is dominated by interface sliding and weak correlated with JRC. For WFJ rock with greater strength, the fracture behavior transition from interface sliding to matrix splitting with increasing JRC. Crack number in both the matrix and the WFL intensifies with increasing JRC and WFJ strength, accompanied by shifts in dominant fracture zones. When WFJ strength exceeds a threshold, the filling becomes more resistant to cracking, suppressing internal failure while amplifying damage in the surrounding matrix.