Study On Dynamic Response Characteristics For Underground Tunnel Structure Under Seismic Wave

With the rapid development of China’s economic construction, the quantity of tunnel and underground engineering which related to highway and railway (including MTR) is getting more and more. The,study on seismic analysis of tunnel and underground engineering has just started in our country. Aseismatic design of tunnel and underground engineering is mainly refer to code for seismic design of the ground building structures. In the Wenchuan earthquake, a lot of tunnel and underground engineerings had been severely damaged and some of them have been unable to repair. This shows that the seismic horizontal load which produced in the actual earthquake is much larger than that of engineering design used. It is obviously inappropriate that seismic design of underground engineering refers to the seismic design of building structures on the ground. Therefore, it is very important to study on the dynamic response and shock absorption measures of the tunnel and underground engineering structure under the seismic wave and the study is carried out from the aspects of theoretical research, numerical simulation, experimental research and engineering application. The main contents include the following aspects:Considering the two-phase coupling action of soil and water, the dynamic response on the cavity structure embedded in saturated soil under seismic wave was analyzed. According to the Biot’s theory of saturated soil and scattering characteristics of seismic wave by cavities, the Green function for the saturated soil with the coupling action of soil and water was derived by using the integral transform method. The boundary element integral equation for seismic wave scattered by cavities embedded in the semi infinite saturated porous was set up. The calculated results show that the stress surrounded the cavity increase2～5times with the propagation of the seismic wave when there are holes in the soil. Therefore, this factor should be considered in aseismatic design of tunnel and underground structure. At the same time, the permeability of the saturated soil has great influence on wave-field scattering. As the compression of saturated soil decreases, the dynamic stress concentration coefficient increases. As the permeability of saturated soil decreases, the dynamic stress concentration coefficient and pore pressure increases.Dynamic response of a circular tunnel lining embedded in the saturated soil subject to seismic P wave is investigated in this study. The surrounding medium of the tunnel is considered as a saturated porous medium and described by Biot’s theory. While the tunnel lining are treated as curved beams described by a curved beam theory, which can account for both rotary and shear deformation. The scattered wave field in the porous medium is obtained by the wave function expansion method. The differential equations governing the vibration of curved beam are discretized by the General Differential Quadrature (GDQ) method. The wave function coefficients in the truncated series can be obtained by using the displacement compatibility conditions between the porous medium and the tunnel lining. In this paper, the displacement compatibility condition between the porous medium and the tunnel is implemented by boundary least square collocation method. Numerical results show that:for low-frequency incident waves, the responses of the liner segments at the incident side and the shelter side are almost symmetrical. With increasing frequency, due to dynamic effects, the responses of the liner pieces at the incident side and the shelter side are not symmetrical anymore. The responses of the incident side tunnel are larger than that of the shelter side tunnel.The dynamic response of pore structure embedded in layered saturated soil under the seismic wave was studied. Due to the geological evolution and other reasons, the soils are hierarchical in practice engineering, so the layered soil model can reflect the features of actual soil.In this paper, dynamic response of tunnel lining structure in layered saturated soil under seismic wave was analyzed by the finite difference method. And as the engineering Background of Pearl River station, Nanchang Metro Line1, the Metro tunnel calculation model was established and the dynamic response of subway tunnel structure was calculated. Some anti-seismic measures were given, which can be provided with the reference for the design and construction.The indoor model test of dynamic response for cavity structure in saturated soil under the seismic wave was done, and at the same time, as the engineering background of Wenquan tunnel, Jiangxi Dujiu highway, the prototype test of dynamic response for tunnel lining structure under the artificial blasting earthquake was performed. The reliable test data provided for theory research and engineering design and construction by comparing the test results with theoretical calculation results.