Deformation Monitoring And Numerical Simulation Analysis Of The Pit Of Huayang North Sation In Chengdu Metri Line 1 South Extension

Foundation engineering plays a crucial role in the process of urban construction. The environment in constructing of subway foundation is more severe than the normal one. And the technical requirement is more demanding as well. The traditional foundation deformation calculation is mostly based on empirical formula,and cannot accurately predict the excavation deformation,which results in a large number of over-conservative design and serious wastes in the design of foundation pit engineering. This thesis takes the subway pit as an example, by studying the excavation of the foundation pit and comparing the actual test results with numerical modeling results in the construction process,this thesis analyzes the influence degree of the excavation on the deformation of the retaining structure and supporting system. And finally we hope to make some contribution in engineering support.Based on the monitoring data obtained from the pit monitoring project of Huayang North Station of Chengdu Metro, this thesis analyzes the monitoring results, draws the horizontal displacement curve of the retaining pile, the internal force variation curve of the retaining pile, and the curve of radial journal bearing. Through these procedures the deformation model of the foundation pit and the deformation law are analyzed. Based on the three-dimensional finite difference simulation software Flac3d, the appropriate constitutive model and parameters are selected to simulate the deformation law of the envelope and the supporting system during excavation. Comparing the test results with simulation analysis results, the conclusions are present as follows:1. The deformation of the foundation pit of the research site belongs to the deep deformation. The lower part of the strata is a layer of strong pebble and moderate mudstone, and the deformation is small. While the upper soil layer is weak silt clay with a large amount of deformation. The largest deformation occurs in the second support structure above the depth of about 4m of silt clay layer.2. When the supporting structure is established during the excavation of the foundation pit, the influence of the axial force on the support structure of the lower support structure is relatively slow. When the lower supporting structure is dismantled, it has a great influence on the axial force variation of the upper supporting structure. At this stage, it is necessary to pay attention to strengthen the monitoring of key parts and prevent the damage of the supporting system.3. Through the numerical simulation analysis, it can be concluded that the surface subsidence deformation around the foundation pit, the deformation of the pile body to the foundation pit and the deformation of the supporting support system are basically consistent with the actual situation. The simulation has some practical guiding significance.4. The results of the test and simulation show that the supporting system of the foundation pit of the station satisfies the requirements of controlling deformation, but it is unreasonable to some extent and should be optimized.