Experimental Analysis of Shield TBM Tunnel Lining Mechanical Behaviour in an Anisotropically-Jointed Rock Mass: Fid-Bau Portal

Experimental Analysis of Shield TBM Tunnel Lining Mechanical Behaviour in an Anisotropically-Jointed Rock Mass

Hu, Xiongyu / Fang, Yong / Walton, Gabriel / He, Chuan

Abstract Jointed rock masses represent a challenging geological environment for tunnel boring machine (TBM) tunneling at great depth. Especially in the case of rock masses that have anisotropic strength and deformation characteristics, the segmental lining is susceptible to asymmetrical loading and local instabilities during tunneling. This paper presents the results of experimental tests and numerical simulations of the interaction between an anisotropic rock mass and the segmental lining of a tunnel. In the tests, we considered different lateral pressure coefficients (σ h /σ v ), joint dip angles, and joint spacings. In the numerical simulations, different joint cohesions, friction angles, and tensile strengths were considered in order to study the effects of joint mechanical parameters on the behaviour of the liner and to evaluate quantitative trends of this effect on the liner. We studied the internal force, deformation, and fracture of the segmental lining. It was shown that, under isotropic in situ stress (σ h /σ v , = 1), the anisotropy of the rock masses was a major control on the deformation and damage of the liner, with the maximum positive bending moment and tensile cracks on the liner developing mainly at the direction normal to the stratification. When loaded by increasingly anisotropic in situ stress states (σ h /σ v > 1), the deformation of the liner and the characteristics of the damage were observed to become increasingly influenced by the major principal stress and, correspondingly, less controlled by the anisotropy of the rock structure. The smaller joint spacing tended to induce larger rock mass pressure on the liner, thereby resulting in greater internal force and deformation of the liner. According to the results of the numerical simulations, the internal force on the liner and its deformation increased markedly with decreasing joint friction angle and cohesion values. The response of the internal force and deformation of the liner to the change in the joint tensile strength was relatively small.