Deformation responses and strength criteria of different shotcrete-rock composites under triaxial cyclic compression

Abstract

Understanding the mechanical performance of shotcrete-rock composites under cyclic loading is important for deep-buried underground projects. In this study, triaxial cyclic compressive tests were conducted on the shotcrete-rock composites (SC-G with granite and SC-S with sandstone) to investigate their cyclic failure mechanisms. The results showed that the confining pressure and rock type both had significant effects on the failure modes of the composite materials. Under triaxial cyclic loading, the failure process of the composites can be divided into five stages. Both the axial and lateral deformations of SC-S were larger than that of SC-G, but the elastic modulus of SC-S was smaller than that of SC-G. Besides, the volumetric deformations of the composites included both contraction and dilation stages, and the plasticity parameter was introduced to establish the dilatancy angle models for shotcrete-rock composites. In addition, considering the damage accumulation during triaxial cyclic loading, a yield surface model was proposed based on the M−C failure criterion to characterize the correlation of post-peak stress state, plasticity parameter, and strength parameters of the composite. The research findings can provide a great theoretical significance and engineering value for the safe design and construction of deep-buried tunnels.