Compression failure conditions of concrete-granite combined body with different roughness interface

Bedrock and concrete lining are typical composite structures in the engineering field and the stability of the geological body and engineering body is directly connected to the mechanical properties of the composite body. Under this background, the study provides the transverse isotropic equivalent model of concrete-granite double-layer composite based on the notion of strain energy equivalence. Assuming that the strength failure of concrete and granite meets the Mohr-Coulomb criterion, then the strength failure model of the combined body considering the joint roughness coefficient (JRC) is derived, and the influences of JRC, the height ratio of concrete to granite, and confining pressure on the strength failure characteristics of the combined body are emphatically analyzed. Finally, the model applicability is illustrated by the uniaxial and triaxial compression tests on concrete monomer, granite monomer and concrete-granite composite samples (CGCSs) with different JRCs. The results revealed that the compressive strength of the composite is closer to the concrete with lower strength in the combined body under different confining pressures. Adding interface roughness causes to raise the compressive strength of the composite due to interfacial adhesion between concrete and granite, and a slowing growth trend is observed in compressive strength as roughness. The model can provide a certain reference for the stability design and evaluation of engineering rock mass.