Abstract
Soil-rock mixtures (S-RMs), as a kind of special engineering geological material, need to be studied because of the special structure and complex movement mechanism of their rock blocks, their physical and mechanical properties, and the factors underlying rock block movement in the process of their deformation and failure. In this paper, a series of discrete-element numerical models are constructed in particle flow code software (PFC2D). First, the random structure numerical models of S-RMs with different rock block proportions are established. Then, the parameters of the soil meso-structure are inversed by the biaxial simulation test, and a series of biaxial compressive tests are performed. The characteristics of stress and strain, deformation and failure, and rock block rotation and energy evolution are systematically investigated. The results show the following. (1) As the rock block proportion (confining pressure 0.5 MPa) increases, the peak strength of increases, the fluctuations of the post-peak become more obvious, and the dilatancy of the sample increases. (2) As the rock block proportion increases, the width of the shear band increases, the distribution of cracks becomes more complex and dispersed, and the range of the shear zone increases. (3) The number of rock blocks with rotation also increases significantly as rock block proportion increases, and the rotation angles are mostly between −5° and 5°. (4) The strain energy of S-RMs with different rock block proportions follows the same change rule as axial strain, showing a trend of first increasing and then decreasing, like the stress–strain curve.
Highlights
As a special geological material, soil-rock mixtures (S-RMs) refer to inhomogeneous mixed media embedded in high-strength rock blocks in a relatively low-strength, finegrained matrix [1,2,3,4,5]
Based on the above simulated biaxial test results, deviatoric stress–axial strain curves were plotted for the S-RM specimens with different rock block proportions (RBPs) (Figure 6)
According to the analysis of the internal structure of the S-RM, the soil plays a major role in the initial stage of stress, and the blocks only bear part of the load, so the rock blocks in the S-RM are wrapped by the soil, the rock blocks are unable to come in direct contact with each other, which is the typical difference between the S-RM and geological materials
Summary
As a special geological material, soil-rock mixtures (S-RMs) refer to inhomogeneous mixed media embedded in high-strength rock blocks in a relatively low-strength, finegrained matrix [1,2,3,4,5]. It is difficult to employ FEM and FDM to accurately depict the deformation and failure characteristics of S-RMs, which are nonhomogeneous, discontinuous materials These two methods cannot be used to determine the mesoscale effects of factors related to rock blocks (e.g., their morphology and proportion) on the progressive failure process. From the perspective of the mesomechanical properties of loose media, the PFC method analyses the macroscopic physical and mechanical behaviour of materials by simulating of the motion and interaction of granular media. This method has considerable advantages for solving problems related to interparticle interactions and large deformations [26,27,28]. Using biaxial tests in PFC2D , a series of numerical analyses were performed to investigate the mechanical behaviours and failure mechanism of the S-RMs with different rock block proportions
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