Urban Subway Tunnels Structure And Soil Seismic Mechanics Performance Analysis In Liquefiable Ground

In the current study of geotechnical engineering, the subject of earthquake liquefaction of saturated liquefiable sandy soil foundation is still a key point in geotechnical research project. In addition, with the development of global economy, the rapid urban expansion, so to build the subway has become essential to the project in a city. When the earthquake struck, the seismic cause the upward displacement and settlement of soil displacement, Due to the concentrate force, the unit of the corner of the subway underground structure extrusion and damage. The subway underground structure once damaged in the earthquake, not only the economic loss is irreparable, and as a hidden underground structure, it is difficult to repair, also may threaten the safety of life. The subway construction has entered a stage of rapid development in China, because the widely range of the subway extension, some subway engineering construction to build in high intensity area, so the study of seismic method not only has important significance to the building of the subway, especially is the stepping stone for the design of the underground structure.This research adopts the finite element program DBLEAVES which can solve the 2 d / 3 d soil and water coupling numerical calculation of dynamic and static problem effectively. It can detailed describe the mechanical properties of soil under the action of seismic wave, including saturated sand and clay's the change of force and liquefaction under cyclic load; This model also introduce the over-consolidated state change parameters, structure attenuation parameters, the anisotropic development speed control parameters; The calculation not only analyzed dynamic response of soil and structure in the process of seismic load, also analyzed the foundation of the long.term consolidation settlement after earthquake.This paper adopts soil and water coupling of two-dimensional finite element analysis method to study earthquake mechanics performance of urban subway tunnels in liquefiable soil, it detailed analysy the deformation of foundation soil and structure, excess pore pressure ratio in saturated soil and the internal force response of the underground structure, excess pore pressure ratio after the earthquake, the change of Long-term displacement of consolidation settlement after earthquake, reveals the mechanism that the elevation of underground structure during the quake and the settlement of soil after the quake.The model discusses that the liquefiable soil thickness, ground water level,the deep of structure,input earthquak wave have influence on the underground structure seismic response and earthquake subsidence and excess pore water pressure ratio. The study results can provide theoretical reference for later anti-liquefaction design research.According to the results of numerical simulation analysis, as the input of earthquake wave and settling time accumulation after the earthquake,the soil element near the underground structure has uplift displacement,the far field element has subsidence displacement and the corners of the underground structure have been different damage. In addition to the earthquake liquefaction of foundation, the earthquake with the dissipation of excess pore water pressure and foundation uneven settlement are important problems that cannot be ignored. And seismic liquefaction and underground structure internal force response also change a lot as liquefied soil layer thickness, the location of the underground water level changing,the direction of earthquake wave input,seismic acceleration and the depth of structure, these factors in underground structure seismic design are also cannot be ignored.