Additional Stress And Settlement Of The Soil Surface Research Caused By Shield Construction Of Subway Tunnel

Abstract:With the rise of the national urban underground rail, metro shield tunnel excavation rapid development due to its broad formation applicability and the economic advantages and become the first choice of major cities in the subway tunnel excavation. As for the research of the impact on the surrounding soil of Shield excavation, and control the impact of surface subsidence settlement and deformation of the surrounding buildings caused by subway tunnel shield excavation. In order to obtain regional shield construction experience, provides the theoretical background for similar formations metro shield tunneling construction to ensure the safety and suitability of the surface building when shield excavation, the analysis for surrounding soil additional stress and surface subsidence patterns caused by shield tunnel excavation is necessary. In this paper, with background of the Confucius Temple to Chang Fu Street in3th interval Line subway tunnel of earth pressure balance shield excavation in Nanjing, using the elasticity theory to research the additional stress on the surrounding soil caused by shield tunnel excavation; Analysis building subsidence and the deformation of the surface which is caused by of shield tunnel excavation in using stochastic medium theory, Peck formulas and numerical analysis, the main contents are as follows:1. Make statistical analysis of shield excavation parameters and surface subsidence values for range segment of shield excavation, and identify the construction quality of soil in the studied section from the results of shield construction statistical analysis; finishing surface excavation range segment vertical and horizontal measuring settlement point measured settlement value to obtained complete field measurement data.2. Combining the shield excavation instance of Confucius Temple to Chang Fu Street right line in Nanjing Metro range Line segment, getting the integration of the shield excavate surface by use of elastic mechanics Mindlin stress formula in the soil solution and point sources and sinks method.Get the distribution area and laws of surrounding soil additional stress caused by shield excavation face additional thrust and friction between the shell and the surrounding soil and the tail soil loss.3. analysis surface ground subsidence five stages of variation shield tunnel excavation by use of longitudinal settlement points subsidence curves generated by the timing of construction when the shield forward. Application Peck formula, stochastic medium theory, use the least squares method, Powell optimization method inversion analysis longitudinal subsidence formula parameters. And calculates shield tunnel excavation transverse surface subsidence curves by useing the results, find the results consistent with the measured values obtained, confirme the correctness of the inversion parameters, and can be used to guide the shield construction. Consider the impact of buildings structural rigidity within the scope of the distribution of surface subsidence trough on the surface subsidence trough. Use the modified Peck formula calculated building settlement curves and with the comparative analysis of Peck calculated surface subsidence curves with engineering examples, reach conslusion that The calculate results of formula Peck closer to the field measured values.4. Analysis additional stress distribution of surrounding soil and its impact on surface subsidenc by application large general-purpose software ABAQUS finite element which establish three-dimensional model shield tunneling step excavation, analysis and contrast theoretical calculations and measured values to guide construction.