Rate Effect on the Direct Shear Behavior of Granite Rock Bridges at Low to Subseismic Shear Rates

Natural faults are often heterogeneous with spatially variable cohesion caused by healing processes. Using rock bridges as laboratory analogs, we investigate how cohesion-healed patches rupture at different shear rates. We performed direct experiments on granite rates from 1 μm/s to 10 mm/s (low subseismic rates), and quantitatively characterized the failure surface morphology integrating laser scanning ArcGIS. The results show a notable dependence of both mechanical morphological characteristics rate. mode transitions tensile low At rates, forms curved coalescence patterns undulating surfaces significant roughness anisotropy. straighter shear-formed observed. In addition, peak strength, anisotropy increase increasing rate within regime. explain observed rate-dependent behaviors energy geometric features micro-cracking mechanisms. suggest through variations in 3D parameters that effects should be incorporated into models fault morphology. all asymmetric, asperities more inclined direction load. find this asymmetry fracture further shearing after failure, it can used determine sense displacement.