Research on mechanical parameters of coarse-grained sliding soil based on CT scanning and numerical tests

The inner structure of sliding soil is quite inhomogeneous, which makes it very hard to investigate the mechanical properties. In this paper, intact sliding soil samples collected from the Huangtupo landslide is verified to be rock and soil aggregates (RSA) firstly. Because of the grain-size limitations for general indoor shear tests and the unpredictability of test data obtained by reshaped sample, a new method which combines CT scanning for undisturbed samples, mechanical tests for fine-grained subdomain and numerical test is proposed. With the advantages of repeatability and parallel comparison, deep research into the mechanical properties and deformation mechanisms for sliding soil is carried out. The research shows that, for the RSA in this paper, which the coarse particles content is about 30 %, fine-grained subdomain is still the frame part of RSA, compared with pure fine-grained soil, the internal friction angle does not obviously increase, but the cohesion increased by at least 80 %. Meanwhile, coupling deformation between coarse particles and fine-grained subdomain is a complex mechanical process; coarse particles will support an effective resistance to the fine fraction, and in Mohr-Coulomb model, it is reflected by obvious increase of cohesion. Based on the mechanical trace preservations on a block of gravel, this external friction effect is verified. Then, by seven groups of large-size stacked ring shear test for the RSA samples, these analyses and judgements are verified. The comprehensive research method can also be widely used in achieving the mechanical and failure characteristic of RSA.