Geomechanical Characterization of Zhangmu Soil-Rock Mixture Deposit

Abstract

Zhangmu deposit is a typical soil-rock mixture (S-RM) deposit made up of very complicated inhomogeneous materials containing soil matrix and rock blocks of various sizes. The slope shows evidences of instability phenomena characterized by shallow landslides and several extensive cracks along slide crown, which seriously affects the life of local residents. In order to characterize the mechanical behavior of the deposit with evaluation of the actual strength parameters and permeability while taking into account the influence of the block proportion, seven test points were established for in situ S-RM and constant-head injection tests on a large scale. The results indicated a larger internal friction angle and lower cohesion for S-RM from in situ tests compared to tests results obtained from laboratory testing. Moreover, it was noted that the strength parameters were correlated with the block proportion by weight (WBP) of S-RM, while both internal friction angle and cohesion were observed to be strongly affected by a critical WBP threshold (70 %), which is in agreement with the common S-RM mechanical behavior. Furthermore, permeability increases with WBP increase to more than 70 %, denoting a similar threshold to the findings observed in strength characteristics.