Experimental and Numerical Investigation of Mechanical Behaviors of Cemented Soil–Rock Mixture

Abstract

In order to reveal the macroscopic mechanical properties and mesoscopic failure mechanism of cemented soil–rock mixture (CSRM, for short) that widely exists in nature, a series of large-scale triaxial tests are carried out. Firstly, specimens of soil–rock mixture without cement and specimens mixed with small amounts of cement are compared to demonstrate that it is necessary to further divide soil–rock mixture into CSRM and uncemented soil–rock mixture. Then, laboratory large-scale triaxial tests on CSRM specimens with different rock block proportion (RBP, for short) are conducted to explore the effect of RBP on the macroscopic mechanical responses of CSRM. Finally, based on the developed three-dimensional discrete element modeling technology for irregularly shaped rock blocks and soil–rock mixture, a numerical simulation of laboratory tests is performed to analyze the mesoscopic failure mechanism of CSRM. The results indicate that CSRM specimen with 3 % cement exhibits strain softening and localization, whose strength and modulus increase dramatically compared with those of specimen without cement. Peak strength and brittleness index of CSRM specimen both are decreased with increasing RBP under the confining pressures of 0.1, 0.2 and 0.3 MPa. In CSRM specimens, microcracks initiate at the soil–rock interfaces, and then propagate in soil matrix bypassing the rock blocks with multiple tortuous failure bands coming into being throughout the specimen eventually. The effect of RBP on strength of CSRM depends on the combination of skeleton-effect of rock blocks and cementation-effect of the specimen.