Study On Stability Of Surrounding Rock In Water-rich Area Of Shuangbei Tunnel Based On Fluid-solid Coupling

The Chongqing Shuangbei Tunnel to cross the water-rich area is taken as the engineering background.The influence of the seepage field of the surrounding rock and stress field interaction on the stability of surrounding rock is studied by using the special section surface monitoring data of the tunnel,the finite element Midas/GTS NX analysis software and the seepage theory of the fractured rock mass as well as combining with the groundwater seepage theory.Under the condition of primary lining full permeable and partially permeable(arch and side wall),the influence law of the control factors of different underground water levels,different tunnel depth and different surrounding rock levels on the stability of surrounding rock and the influence law of pore water pressure on the primary lining are discussed.At the same time,the surrounding rock stress,displacement deformation,plastic zone of surrounding rock and primary lining stress as the carrier,quantify the influence of various control factors on the stability of surrounding rock.The specific research contents are as follows:(1)Combining the seepage theory of crack water and the theory of hydraulics,the interaction relationship between seepage field and stress field in the rock mass of Shuangbei tunnel to water-rich area is discussed.The seepage-stress coupling equations and finite element calculation equations of the rock mass in the water-rich area of the Shuangbei tunnel is given.(2)By analyzing the mechanism and mode of fluid-solid coupling of surrounding rock,it is concluded that the surrounding rock stress field affects the surrounding rock seepage field by changing the permeability coefficient K and the water storage coefficient S of the surrounding rock;the surrounding rock seepage field reduces the surrounding rock physical parameters to influence the surrounding rock stress field by the chemistry erosion,physical weakening effects and mechanical effects.(3)Select the special section of the water-rich zone of Shuangbei Tunnel,under the not considering the fluid-solid coupling and considering the fluid-solid coupling.The change rule and increasing trend of surrounding rock stress,displacement and deformation,plastic zone of surrounding rock as well as primary lining stress are obtained by finite element Midas/GTS NX analysis software.(4)On the basis of considering fluid-solid coupling,in the full and partial water permeability of the primary lining,the influence of some control factors such as the depth of underground water level tunnel and the level of surrounding rock on the stability of surrounding rock in the special section of Shuangbei tunnel in the water-rich area is analyzed.In the case of full water permeable,the dividing line of various control factors changes is 4D(D is the hole diameter);in the case of partial water permeable,the dividing line of various control factors changes is 3D(D is the hole diameter).At the same time,the influence law of various control factors on the stability of surrounding rock is obtained.(5)Numerical calculation of the karst water-rich section of the Shuangbei tunnel and comparison with the tunnel monitoring data,analyze the stability of the surrounding rock during the construction process and the stress of the supporting structure,and verify the numerical simulation reliability.At the same time,it provides theoretical basis for design and construction for similar projects.