Dynamic and fracture behavior of the filled jointed rock after freeze-thaw cycle damage: experimental and numerical studies

In cold regions, rock masses are inevitably subjected to the combined effects of freeze-thaw cycles and dynamic loads. As weak structural planes in rock masses, filled joints are particularly susceptible to damage under these conditions, resulting in reduced dynamic strength and overall stability. Consequently, understanding the dynamic response of filled jointed rock masses under freeze-thaw cycling requires focused research attention. To investigate damage evolution and dynamic response in filled jointed rock masses under freeze-thaw cycling, a numerical model was established for Split Hopkinson Pressure Bar (SHPB) dynamic impact testing by coupling the finite difference method and discrete element method, informed by laboratory SHPB impact test data on filled jointed rock specimens. Crack propagation patterns and failure modes have been analyzed across varying numbers of freeze-thaw cycles, alongside a parametric study on joint dip angles and thicknesses. A progressive shift in specimen failure mode from tensile-dominated to shear-dominated under increasing freeze-thaw cycles. Both peak strength and elastic modulus display a U-shaped variation relative to joint dip angle yet decrease with greater joint thickness. As the dip angle of the filled joint increases, both the crack initiation stress and the total number of cracks exhibit a distinct U-shaped variation, initially decreasing before subsequently increasing. In contrast, the total number of cracks shows a continuous increase with greater thickness of the filled joint. Reduced filled joint thickness promotes shear-dominated failure modes, while joint dip angle variations most significantly affect the orientation of cracks between 0° to 60° and 120° to 180°. Notably, specimens with a 30° joint dip angle exhibit peak failure susceptibility.