Mechanical Characteristics Of The Rock-socketed Diaphragm Wall In Confined Water Layer During The Whole Process Of The Construction

In the process of urban development and construction, a large number of deep foundation pit projects have been produced, and the scale and depth of each excavation has been increased continuously. There is confined water in the deep foundation pit engineering near the river under the condition of multivariate strata in all likelihood. It is the most reliable method to prevent the hydraulic connection between inside and outside of deep foundation pit when rock-socketed deep diaphragm wall is used. However, less study has been done on this kind of diaphragm wall. The force system of the diaphragm wall cannot be same as that in the multi-channel supported situation under different excavation conditions, so it is necessary to analyze the stress characteristics during the whole process.Combined with deep foundation pit engineering of Wuhan Greenland Center, model test and numerical simulation were used to analyze mechanical characteristics of the diaphragm wall during the whole process of the construction in this paper.Step-by-step excavation, installation of supporting system, simulation of confined water strata and data acquisition of the whole construction process of wall body's stress deformation were realized via the model test designed. Besides, the mechanical characteristics of the diaphragm wall under different confined water conditions were analyzed. The test results show that the deformation shape of the diaphragm wall is parabolic and central extrude,and the active earth pressure behind the wall gradually decreases with the excavation. The existence of confined water can increase the displacement and deflection of the wall as well as the redistribution of the earth pressure behind it.Therefore, earth pressure presents "Two ends big, middle small" state. The bending moment of the diaphragm wall increases sharply with confined water, the bending moment distribution is closely related to the support system of the wall. Outer surfaces of foundation pit are tensioned within the excavation depth range and the maximum bending moment is on this kind of surfaces. In the meanwhile, the maximum bending moment on inner surfaces of foundation pit appears in fixed-end.MIDAS/GTS was used to explore the relevant properties of rock-socketed diaphragm wall in confined water layer. Considering the convenience of the finite element software, finite element analysis was made to verify the result of one model experiment, and necessary supplement was proposed for factors which were not considered in the model test. Simulation results show that the finite element calculation results are close to the experimental results. The effects of practical processes of stepped excavation and construction of supporting system were considered in numerical simulation of deep foundation pit engineering in Wuhan Greenland Center. Regularities of the earth pressure behind the wall and the deformation of wall body were obtained and comparison was made between numerical simulation results and model test results. At the same time, the working condition of the non-confined water was simulated.Combined with deep foundation pit engineering of Wuhan Greenland Center, monitoring system was set up for deep foundation pit braced by rock-socketed diaphragm wall in confined water layer. Combined with the monitoring results, analysis was made to verify the conclusions in this paper and some improvement measures were put forward.In summary, the model test and numerical simulation were used to analyze mechanical characteristics of the rock-socketed diaphragm wall during the whole process of the construction in this paper. Application and verification were made combined with the actual project.The research results have certain reference value for similar deep foundation pit engineering.