Excavation unloading response of cylindrical rock-like specimen with axial joints: laboratory experiment and numerical simulation

Joints have a significant influence on the deformation and failure mechanism of the surrounding rock. To reveal the influence of axial joint on mechanical response of the roadway surrounding rock after excavation unloading, the deformation and failure characteristics of cylindrical rock-like specimen (CRLS) with an axial joint was studied through laboratory tests and numerical simulation. Also, the influence of joint size and position on strain variation, secondary stress evolution and plastic zone distribution of the CRLS were analyzed. Results show that the axial joint can promote the deformation of the surrounding rock on the inner side of the joint, while hindering the deformation of the surrounding rock of the roadway on the outer side of the joint. In addition, the size and position of the axial joint have a significant influence on the distribution of secondary stress and plastic zone of the surrounding rock. The stress relief zone is mainly located between the joint and the excavation profile, whereas the plastic zone is mainly distributed at both ends of the joint and between the joint and the excavation profile. Finally, the tangential stress concentration can be alleviated by choosing proper distance between the joints and the roadway, and the failure mode of the surrounding rock between the joint and the excavation profile transmitted from tensile failure to shear failure with the axial joint moves away from the roadway. The research results could provide technical reference for roadway support and disaster prevention in a deep jointed rock mass.