Stress Analysis And Application Research Of Section Steel TRD Supporting Structure

The equal thickness cement-soil mixing wall technology was first developed and applied in Japan in 1994,and has been widely used in China in recent years.The results have been remarkable for dealing with the issue of the rail transit foundation pit engineering with confined water and strong permeable layer in the depth range of foundation pit excavation,and for the surrounding complex municipal pipelines and the protection of ancient buildings.The application of this method in China will be summarized.It will conclude that the most significant advantage of TRD method over traditional SMW pile and ultra-deep diaphragm wall lies in its excellent water-proof performance,uniform wall continuity and equal spacing of inserting section steel.The experimental results of the present study show that the fly ash-mineral powder composite cement-soil material has better strength and impermeability;can improve the strength of cement-soil and replace a certain amount of cement;improve the utilization of solid waste and reduce the impact on the environment.This provides a reference for the optimization of the mix ratio of TRD method.On the basis of existing foundation pit projects using SMW method,a finite element model of foundation pit excavation and support based on residual stress theory has been simulated.In order to investigate the possible outcomes of using the TRD method as oppose to SMW method the method parameters were replaced.The present study compared the simulated values of horizontal displacement of retaining wall,settlement of surrounding roads and support resistance with the measured values under different working conditions.The finite element results show that the TRD method can reduce the horizontal displacement and surface settlement of the retaining wall to a certain extent,and the horizontal displacement and surface settlement of the retaining structure are further reduced after the section steel is equidistant.Elastic foundation beam method and finite element method are used to analyze the stress of the retaining system.The analysis of lateral foundation reaction method shows that the flexural rigidity of the wall by TRD method is almost unchanged compared with the traditional SMW method.The flexural rigidity of the wall increases to a certain extent and the horizontal displacement of the retaining wall decreases when the section steel is set at equal spacing.Finite element software was used to calculate and analyze the following: the load-bearing deformation shape of traditional SMW method and TRD construction method;the stress deformation of enclosure structure before and after the equal spacing of section steel;the bending moment;stress distribution of section steel and cement-soil and finally the change of support resistance.The new TRD method along with equal spacing of section steel reduces the local shear weak surface.This has a high contribution rate of cement-soil stiffness,uniform horizontal force,and more coordinated deformation of section steel and cement-soil under external force.It could be argued that it is better than the traditional SMW method for the safety and stability of the structure.In the finite element model,the influence of TRD method on the deformation of TRD retaining structure is further analized after the change of wall material properties and internal support stiffness.