Deformation, damage, and collapse of phyllite tunnels under strong earthquake dynamic actions

In this work, through analyzing the effects of large deformation, lining damage and collapses, which happen frequently in the soft rock tunnels in the Guang-Gan Expressway, the characteristics and causes of the geological disasters for the soft-rock tunnels are investigated. The results show that the large deformation and collapses occur near the vault and tunnel face. The poor mechanical properties and weak self-bearing capacity of the surrounding rock and the softening caused by the groundwater are important factors for the disasters. The lack of experience in design and construction in the meizoseismal area and the aftershocks are other important factors. The field test indicates that three benches and the reserved core soil construction method should be applied to control the stability of the broken phyllite tunnels, and the key technology should be strictly controlled during the construction. In particular, increasing the stiffness of the supporting structure and enclosing of the lining in time are efficient methods to control the large deformation and collapses in crushing soft-rock tunnels in the meizoseismal areas.