Real-time ultrasonic experiments and mechanical properties of soil and rock mixture during triaxial deformation

Non-linear mechanical behaviours of soil and rock mixture (SRM) are known to be the result of elasticity mismatch between soil matrix and rock blocks. Yet the rock–soil interactions, rock block interlocking phenomenon and their dependence under triaxial deformation are poorly understood. Here the authors investigate on the mechanical and ultrasonic properties of SRM by analysing the variation of ultrasonic pulse velocity (UPV) during triaxial compression. The results show that rock–soil interaction can be reflected by the variation of UPV during deformation. In this work, the change of UPV mainly depends on the axial stress level, and they present a consistent trend during deformation. With the increasing rock block percentage, both axial stress and UPV take on the fluctuation growth trend; the fluctuation is most obvious at the strain hardening stage. Internal friction angle increases with the increasing of rock block percentage, while the cohesion presents the opposite trend. The ultimate failure modes and crack coalescence behaviour were also evaluated, with the increasing rock blockpercentage, failure mode of SRM experiences such as shear failure and bulging failure.