Complex Formation Underwater Shield Tunnel Seismic Response Analysis

With the underground engineering technology is improving daily, Shield method of construction are increasingly being applied to the underwater cross-river tunnel construction. However, our country, China land in the circum-Pacific seismic belt, seismic activity is very frequent, therefore, focusing on the research and improvement of seismic response analysis methods of shield tunnel has great significance. This paper rely on issue that Structural statics-kinetics feature and key technical parameters research of Shiziyang underwater tunnel, which is scientific research and development program topic of the Ministry of Railways, with Shiziyang tunnel in Guangzhou-Shenzhen-HongKong passenger dedicated line for engineering background, use finite difference method, analyse shock absorption measures of typical working conditions. The main contents are as following:1. Establish two-dimensional numerical model, choose two typical corss-sections of the saturated sand and soft soil, analyse the earthquake response of the structure and the surrounding strata under different seismic waves of these corss-sections. The resules show that the internal forces and displacements under different seismic waves are required to meet the safe operation of the structure. And the fine sand layer at the top of the tunnel will liquefy, but does not pose a threat to the stability of the structure.2. For the saturated sand section, discussed the dynamic response of the structure and the surrounding strata under different incidence directions of seismic wave, and research shock absorption effects of different parameters of oundation. Results show that horizontal incident seismic wave has greater impact on the structure and the soil pore water pressure. And the greater the scope of foundation reinforcement and the higher foundation strength parameters improvement, the stronger of the ability of soil to resistant liquefy, more internal forces and deformation to reduce. 3. Establish three-dimensional numerical model, analyse the dynamic response feature of the structure and the surrounding strata under different seismic waves and different incidence directions of the intersection structure of main tunnel and connected aisle. Calculation show that the structure deformation and stress under different seismic waves are required to meet the require of seismic fortification, the fine sand layer at the top of the tunnel will liquefy, but does not affect the safety of the structural. And horizontal incident seismic wave has greater impact on the intersection structure.4. Use three-dimensional numerical method, analyse the dynamic response of the structure under different incidence directions of seismic wave of space crossing structure by which working shaft is connected with shield tunnel and open cut tunnel. Results show that individual parts of the working shaft and tunnel junction structure occurs a greater tensile stress during earthquake, exceeds the structural design value of tensile strength, with a certain degree of risk of earthquake damage. And horizontal incident seismic wave has greater danger on the intersection structure.