| With the rapid development of the national economic, and the continuous improvement of urbanization rate, a huge traffic pressure have been taken as lots of rural population moving into the city. In order to solve this problem, more and more metro constructions are builded in the cities. Engineering problems that caused by groundwater are usually encountered in the construction of underground railway, such as sudden gushing mud disaster.In the southeast coastal areas in China,many engineering problems are frequently occurred in the construction of the subway in such formation with saturated sand, belonging to the groundwater and soil coupling problems, with the characteristic of loose structure and noncoherent,which may cause collapse as the layer are excavated.So,how to analyze failure mechanisms of tunnel surrounding rock with the saturated sand under different hydraulic conditions and putting forward some protection and reinforcement measure have been taking a very important theoretical and practical significance.Several researches aiming at the Above Problems are done as following in this paper:1.In this paper, a large number of investigation of relevant issues and literature are made for the physical and mechanical properties of saturated sand layer, as well as the summary for diversified methods of the fluid-structure coupling simulation on the saturated sand layer by using particle flow method; The method for determining the basic principles, counting processn and relevant physical parameters are focused on in this paper, as well as various constitutive model and related parameters in the particle flow method. Due to the discrete characteristics of sandy soil and low viscosity between the sand, the contact stiffness model is adopted to simulate the deformation characteristics of saturated sand tunnel. 2.The correlation theory and implementation method of PFC2D which are used to practice the Fluid-structure coupling simulation with the particle flow method have been elaborated in consideration of the sand-water structure interaction. And the Driving force formula and pressure gradient formula for the N-S incompressible fluid, whose density are Constant,are inferred by dividing the fluid by fixed grid.3.By adopting the two-dimensional particle flow simulation program PFC2D the stability of the shallow tunnel surrounding rock with the saturated sand layer in Guangzhou metro line5from the ZhuJiang new town to LieDe have been simulated and analyzed. The deformation and failure of the surrounding rock are taken into account in different working condition:①Don’t regard the groundwater seepage②Regard the groundwater seepage, and analyzed the difference between the tunnel surrounding rock deformation and failure under two kinds of permeability coefficient.4.The form of deformation and failure of the face of the Shield tunnel excavation with the saturated sand layer in different penetration rate have been analyzed by PFC2D. Simulation of the actual size of the horizontal permeability conditions left underground infiltration size of1.73e-5mls, receive the whole process of deformation and destruction law and its internal stress change rule of shield tunnel soil front of excavation face. And verify the longitudinal relaxation length formula front of shield tunnel excavation face. |
