Abstract: The mechanical behavior of soil-rock mixtures is strongly influenced by the volumetric block proportion(VBP). In soft rock-weathered soil-rock mixtures,the brittle nature of the rock blocks further complicates their mechanical response. This study employed CT scanning to reconstruct three-dimensional block models and developed an efficient fine-scale discrete element modeling approach that incorporates realistic block morphology and block breakage. Numerical direct shear tests were performed under varying VBP conditions to analyze macro-and meso-mechanical characteristics,revealing the influence of VBP on shear dilation and shear strength in soft rock-weathered soil-rock mixtures. The results indicate that with increasing VBP,the shear strength,dilation,block rotation,block interlocking force,degree of block breakage,frictional energy dissipation,cohesion,and internal friction angle all increase. Block rotation enhances mixture dilation,while increased interlocking between blocks contributes to shear strength; however,block breakage tends to reduce both dilation and strength. Under low normal stress,dilation is primarily governed by block rotation,and shear strength is mainly controlled by block interlocking. Under high normal stress,severe breakage of soft rock blocks reduces the rate at which shear strength and maximum dilation increase with rising VBP.