Research On The Performance Of Supporting Structure Of Grid Underground Wall In Seaside Tunnel

In recent years,with the increase development of underground space,many new maintenance structures have emerged and the grid underground wall is one of them.Due to its unique geometric structure,the grid underground wall has a large overall rigidity and does not require an internal support system.It can better control the deformation of the foundation pit and can also be used as a permanent structure.The main research content of this article is as follows:Firstly,the equivalent stiffness model is proposed.Through the equivalent stiffness model,the whole force of the wall is analyzed and the force of each wall of the grid underground wall is analyzed.The distribution of internal forces in each wall is obtained.By finding the rotation angle α,the overall deformation at any depth z in the grid underground wall can be obtained.Through the horizontal bending moment and shear force analysis of front longitudinal wall under earth pressure,assuming the bending rigidity of the front longitudinal wall,the mid-span deflection of the front longitudinal wall under static earth pressure between the walls is obtained.The total deformation of the wall can be obtained by adding the total deformation and the local deformation.Secondly,based on geotechnical engineering finite element software PLAXIS 3D,the stress and deformation of the supporting structure of grid underground wall were studied.The basic principle of the finite element method and the constitutive model of rock and soil are systematically introduced.A quasi-plane model and a three-dimensional integral model of grid underground wall are established.The stress and deformation characteristics and the space effect of the grid underground wall are systematic studied.The simulation results show that the overall rigidity of the grid underground wall is large,and Lateral deformation at different cross sections is basically the same.Lateral horizontal deformation is largest at the top of the wall and decreases linearly in the direction of the depth,showing an overall tilting deformation,similar to the typical cantilevered support structure.The distribution of the axial force of the wall of the grid underground wall presents that the front longitudinal wall is pressed and the maximum compressive stress is at the bottom of the front longitudinal wall,and the rear longitudinal wall is pulled,the maximum tensile stress is at the bottom of the rear longitudinal wall.The partition wall presents a transitional state.There is a positive bending moment at the junction between the front longitudinal wall and the partition wall.The front longitudinal wall has a negative bending moment due to the earth pressure of the soil between the walls.Thirdly,the parametric sensitivity analysis was performed on the distance wall.The embedded depth of the front and rear longitudinal walls of the grid underground wall,the distance of the partition walls,the thickness of the wall,and the length of the partition wall were systematically studied for the effect of overall deformation and local deformation of the grid underground wall.The results show that the embedded depth has the greatest effect on the overall deformation of the grid underground wall.The length parameter of the partition is the key parameter that affects the overall stiffness of the grid underground wall.Its improvement can significantly increase the overall rigidity of the grid underground wall and reduce the overall deformation of it.Only two parameters,the distance of the partition walls and the thickness of the wall affect the local deformation of the grid underground wall.Local deformation size has three-time relationship with the distance of partition walls and wall thickness ratio B/d1.Finally,the stability and deformation characteristics of the wall under seaward loading are analyzed.The results show that the anti-overturning stability coefficient is higher when the wave thrust is acting,and the anti-overturning stability is lower when the wave pulling force acts.The influence of wave force on the stability of grid underground walls must be considered.The change of groundwater level caused by tidal phenomena also has some impact on the stability of overturning,but it has little impact.The wave load has no effect on the overall horizontal deformation of the grid underground wall.The horizontal frost heave force slightly increases the overall deformation of the grid underground wall.Tidal effects have the largest effect on wall deformation.