Mechanical Response of Deep-buried Tunnels through Soft and Cracked Rock Mass under Different Excavation Methods

The study focuses on the problem that weak surrounding rock of a deep-buried tunnel tends to collapse during the process of excavation,and utilizes Finite Difference Method(FDM) software package FLAC3D numerically in three-dimensional to simulate the construction process of the tunnel with four kinds of excavation schemes which are full-face method,bench method,ring-opening and core-retaining excavation method and center-diaphragm method,with the condition of same supporting structure type and parameters.The mechanical responses of surrounding rock and supporting structure under the four kinds of excavation schemes are analyzed.In particular,more attention is paid to the displacement pattern of the target section,stability of the tunnel face and stress distribution of the supporting structure.Based on the simulation results,the optimum selection is made among the aforementioned excavation schemes.The conclusions can be drawn that center-diaphragm method is best in controlling deformation and stress of surrounding rock;ring-opening and core-retaining excavation method is the most applicable to deep-buried weak rock;the heave of the invert should be regarded as one of the major criterion for surrounding rock stability under high geo-stress and large deformation;the effect of vertical stress on supporting structure is more obvious than the effect of the horizontal stress when excavating in the deep-buried tunnel.