Experimental study on the shear performance of an anchor cable with a C-shaped tube anchored flat structural plane

To analyse the influence of normal stress (σ_n) and steel tube strength on an anchor cable with a C-shaped tube (ACC), we selected Q235 steel tubes and Q345 steel tubes as representative ACCs and carried out double shear tests of ACC-reinforced jointed rock masses. Based on the test results, the influence of the steel tube strength on the ACC axial force and shear force under different normal stresses, the characteristics of the shear force-shear displacement curve of the anchored flat structural plane (FSP) in the rock mass, and the ACC failure mode and contribution to the anchored concrete surface shear strength were studied. The test results show that under 2 ~ 10 MPa of σ_n, the failure angle varies between 28° and 40° due to the bending of the ACC near the structural plane and increases with increasing σ_n. Compared with Q235-ACC, Q345-ACC contributes more to the shear strength of the structural plane and can better exert its axial force when resisting the lateral shearing action of the structural plane. Additionally, we proved that σ_n is a main factor affecting the shear stiffness of the structural plane and that the Q345 C-shaped tube effectively improves the shear stiffness of an ACC-reinforced jointed rock mass and can more fully mobilize the anchor cable during shearing ductility in the tangential direction compared to the performance of the Q235 C-shaped tube. The research results can provide a reference for the further application of ACCs to roadways.