Numerical simulation of strong water-rich silty sand tunnel surrounding rock based on fluid-structure coupling and its application

Abstract

In order to study the rock stability of semi-diagenetic tunnel in strong water-rich and weakly cemented fine sand, based on the fluid-solid coupling theory, taking the Wangjiazhai tunnel as an example, the seepage field, displacement field, stress field variation law and initial support stress characteristics during tunnel construction are analyzed. The result show that:(1) When considering the coupling effect, the maximum subsidence value of the tunnel vault reaches 12.6 mm, and the horizontal displacement of the tunnel body reaches 4.07 mm; regardless of whether the fluid-solid coupling is considered, the distribution characteristics of the contact stress between the surrounding rock and the initial support are similar; the pressure in the surrounding rock, taking into account the fluid-solid coupling effect, is greater than that without taking into account the fluid-solid coupling effect.(2) During tunnel excavation, the pore water pressure map is roughly funnel shaped. The contours of the pore water pressure values near the palm face are dense, with obvious seepage effects.(3) The simulation result show that the underground seepage gathers to the excavation surface, which is consistent with the occurrence of groundwater and inrush in the actual excavation of the tunnel.(4) According to the calculation result of seepage, displacement and stress after the excavation of the simulated tunnel, corresponding preventive measures are taken in the subsequent tunnel construction process to ensure the construction progress and safety of the project.It shows that it is feasible to simulate and analyze the stability of surrounding rock of water-rich tunnel by this method, which provides a theoretical basis for the stability analysis and preventive treatment of surrounding rock of water-rich tunnel.

Keywords

fluid-solid coupling / water-rich tunnel / weak surrounding rock / stability analysis / numerical simulation