Analytical Study On Pore Water Pressure Response Of Soil Around Suspended Foundation Pit Under Water Level Fluctuation

The deep foundation pit engineering in coastal and riverside areas is easily affected by the water level fluctuation caused by wave and tide due to its proximity to the water area.The dynamic water environment has a certain impact on the deformation and stability of the foundation pit engineering.It is necessary to study the pore water pressure response law of the soil around the foundation pit.At present,the research of suspended foundation pit mostly is studied by numerical simulation method,while the analytical research is often based on the assumption of single-layer foundation soil,and mostly are implicit and semi analytical solutions.In this thesis,the explicit analytical solution of two-dimensional pore pressure of soil around the foundation pit is derived by using the analytical method,the response law of pore pressure is analyzed,the parameter analysis of influencing factors,the calculation of water pressure and impermeability stability of supporting structure are carried out,and the analytical solution in this thesis is compared with the equivalent method.The main work and research results are as follows:(1)The seepage field around the foundation pit is divided into three regular regions.Using the separated variable method,the idea of pattern matching and the continuous conditions between regions,the explicit analytical solution of pore pressure around the single-layer soil of foundation pit which considering permeability isotropy and anisotropy under water level fluctuation is deduced.The correctness of analytical solutions is verified by comparison with the finite element numerical calculation results,and the parameters such as the soil permeability coefficient,the permeability anisotropy coefficient,the foundation pit width,the distance from the bottom of retaining wall to impermeable layer are analyzed.(2)For the layered heterogeneous soil foundation pit,the overall seepage field is divided into regular areas,and then the soil in each area is further divided into multi-layer soil layers.The pore pressure solution in each area is expanded by the separated variable method.The matching relationship is established according to the continuous conditions at the regional interface.The explicit analytical solution of pore pressure around the isotropic layered soil of foundation pit under water level fluctuation is deduced,which is compared with the finite element numerical calculation results to verify its correctness,and the parameters such as the layer distribution of foundation soil,the foundation pit width and the retaining wall embedded depth are analyzed.(3)The calculation method of water pressure of retaining wall and a new method was proposed to assess the seepage stability considering the groundwater level fluctuation are studied.Compared with the standard method,the shortcomings of the current standard and simplified algorithm are pointed out.The analytical method of layered soil foundation pit in this thesis is compared with the equivalent permeability coefficient method,in order to provide some reference for practical engineering.