A study of the effect of rock content on mechanical properties of soil-soft rock mixture

The soil-rock mixture (S-RM) with soft rock block is widely used to be form fill slopes in southwest China. The mechanical properties and the soft block breakage properties of the S-RM are much different from the S-RM with high strength rock blocks previously studied. Based on large-scale shear test with different block proportion by weight (WBP) of S-RM, the mechanical properties of soil-soft rock mixture with different WBP are examined. Based on the sieving test before and after shear test, the breakage properties of soft rock blocks are studied. The results show that with the increasing WBP, the shear strength of S-RM increases and the strain-hardening phenomenon is more obvious when the density of S-RM samples are the same. The cohesive of S-RM increases linearly with the increasing WBP, and the internal frictional angle of S-RM also increases linearly when the WBP in the range of 20%~60%. The soft rock blocks occurs breakage in the failure process of S-RM. Under the same normal stress, the breakage ratio of rock blocks increases with the increasing WBP. The breakage ratio of rock blocks increases exponentially with the increasing internal frictional angle of S-RM, indicating that the breakage degree of rock blocks is higher when the biting between rock blocks is larger.