Numerical investigation of the composite mechanical behavior of grouted rock members with rough fractures

Incomplete grout filling in natural rough fractures is common in grouting practices and alters the mechanical behavior of rock masses. This study numerically simulates slurry diffusion in fractures with different joint roughness coefficients (JRC). Rock models with varying roughness and filling degrees are tested under uniaxial compression and constant normal stiffness (CNS) direct shear. Results show that uniaxial compressive strength depends weakly on filling level but strongly on roughness. Higher roughness intensifies stress concentration, accelerates grout damage, and reduces stress transfer, lowering compressive strength. Incomplete filling only induces local stress behind the grout front, slightly reducing bearing capacity. Under CNS direct shear, peak shear strength increases with both filling level and roughness, with filling showing a more linear effect. Residual shear strength is mainly controlled by roughness and can exceed peak strength at high roughness due to asperity interlocking and grout dilation. These findings highlight the key role of fracture roughness in partially grouted rock masses and aid strength evaluation in real grouting conditions.