Laboratory model test study of pullout mechanism of tunnel anchorage

A laboratory model test of tunnel anchorage was conducted to investigate its pullout mechanism and bearing capacity. First, a laboratory model test device was designed and produced. Second, through the strength and deformation test, the material ratio was determined to simulate tunnel rock. Third, the surface and rock deformation, strain and stress were measured during the entire test process. The results show that, under pulling loads, tensile failure first occurs in top surface rock near the anchorage, then shear failure occurs in the rock around the anchorage. The failure surface is inverted cone from the anchorage bottom. The bearing capacity of the tunnel anchorage consists of two parts. The first part is the ultimate friction resistance in the interface of anchorage and rock while the second part is the rock shear-tensile resistance-namely clamping effect. Under 50 times design cable force, the tunnel rock is in elastic stage, suggesting that the current tunnel anchorage design is quite conservative and can be further optimized. ©, 2015, Shanghai Jiao Tong University. All right reserved.