Research On Analysis And Topology Optimization Method For Retaining And Protection Structure In Long-narrow Deep Foundation Pit With Strut And Diaphragm Wall

For some deep foundation pit projects, which the geological conditions are complex and the surrounding ground buildings and underground buildings’ structures are complex, the retaining and protecting for foundation excavation for structures can only choose the strut. This thesis focuses on the study of the finite element analysis method of supporting structure in diaphragm walll of foundation pit and topology optimization method of the strut. This thesis also takes one foundation pit engineering of Nanjing Metro as an example, the engineering adopt the open cut method, using the strut with diaphragm wall for retaining and protecting for foundation excavation. To establish a model of the supporting and protecting structures in diaphragm wall using ANSYS APDL, modeling command stream parameterization.Analysis methods is using M method to calculate and analyze the retaining and protecting for foundation excavation; transform lateral earth pressure into active earth pressure, calculating with combined calculation of soil and water Topology optimization method is using Discrete Variable Optimization Method; using retaining and protecting for foundation excavation material dosage as objective function; the optimization variables are continuous wall thickness、horizontal spacing of the strut、the vertical spacing of the strut.Discussion on the optimization variables will using the enumeration method, by controlling the optimization variables to analysis the displacement relationship of the plate thickness、strut level、vertical spacing and structure. Utilizing orthogonal experiment method to list optimization schemes, and then using horizontal displacement、bending moment、allowable value of shear force to choose the feasibility optimization schemes. Finally Compared material usage to select the optimal scheme.By comparing the numerical simulation can found when the strut wall thickness is greater than 1m, the influence of structure displacement become smaller, and the displacement values tend to be fixed. When changed horizontal spacing and vertical spacing of the internal support, the influence of the horizontal spacing is greater than the vertical spacing to the change of the displacement value of the structure.