Effect Of The Earthquake On The Shield-driven Tunnel

Subway plays an irreplaceable role in the transportation of most developed areas in the world. For a long time, it has been considered that underground structure has fairly strong seismic resistance. Until the year of 1995 when the large scale underground structures of subway stations and tunnels suffered serious destroy in an earthquake in southern Kobe county of Japan, there comes an upsurge in the research of seismic influence on underground structure. Among the seismic research methods of shield-driven tunnel, the quasi-static method and the response displace method are recommended ones in the foreign countries' aseismatic criteria by now for their convenience and easy handling.Because of its location on the circum-Pacific seismic belt, China suffers frequent earthquakes. However, it doesn't set up its own aseismatic criteria for underground structure. Therefore it is of certain significance to do aseismatic research on shield-driven tunnel.The effects of earthquake on shield-driven tunnel can be grouped into two categories: ground shaking and ground failure. The former can produce axial compression/extension and bending moment in the longitudinal direction and shear force in transverse direction of the tunnel while the latter includes liquefaction, slope instability and fault displacement, which cause the tunnel to deform correspondingly.First of all, the influence on the longitudinal effective rigidity of the prestressing force of the blot and tunnel's interaction with the soil is considered, Then, the behavior of a tunnel is approximated to that of an elastic beam subject to deformations imposed by the surrounding ground. The maximal axial compression /extension force and longitudinal bending moment of the tunnel in an earthquake can be calculated, as well as the force and displacement of the blots and the concrete.Secondly, in the transverse section the equivalence of liner to a continuous ring is in common use in the design of the tunnel, while the ratio of the liner effective rigidity is a very important parameter. At the present time most of the literatures are concerned on the ratio of the liner effective rigidity under the weight of the soilcovering above the tunnel regardless of the force caused by earthquake. In this thesis, the method of the equivalence of liner to a continuous ring is used for calculating the ratio of the liner effective rigidity under the weight of the soil covering above the tunnel and the shear force caused by earthquake.Thirdly, the influence on the ratio of the liner effective rigidity of parameters of the tunnel that include the bolt rigidity, the soil resistance, the bolt distribution, the bolt number, the liner radius and the liner thickness, is also studied, with a stress on that of the shear force caused by the earthquake. As a result some useful conclusions are found.Finally, this thesis from an elastic beam model deduces the curve of tunnel sediment brought by the stratum's uneven sediment from fault displacement of the ground as well as the longitudinal bending moment, longitudinal shear force and shear force transformed in longitudinal direction by the tunnel sediment. Besides, it researches on internal force and displacement of tunnel's cross section by shear force transformed in longitudinal direction to build a tie between longitudinal and transverse seismic resistance of tunnels.