Research On The Stratum Deoformation Prediction Induced By Metro Shield Tunnel Construction

With the rapid development of urban construction in our country, the subwayconstruction is an important part of urban underground space development in the21stcentury. Shield method has been widely applied to the urban subway construction, sinceit has some advantages. There are strong adaptation, high speed and ensure the qualityof shield construction. But the shield construction inevitably causes ground movementand deformation, and it will bring a series of engineering problems. Therefore, it isnecessary to predict the stratum deformation caused by shield construction. Toformulate the corresponding control measures to prevent the engineering accidents, soas ensure to reduce the influence of environmental caused by shield construction to theleast extent.In this paper, application of elastic mechanics theory to solve in tunnelexcavation deformation. And combined with the numerical simulation and site actualmeasurement method, the stratum deformation caused by shield construction predictionis studied. The main research contents and achievements are as follows.（1）Review of the development of shield tunnel in the world and the applicationstatus in China, and the prediction methods of stratum deformation caused by shieldconstruction are summarized.（2）Here to recapitulate is a theory of elastic solution of tunnel excavationdeformation problems. In two aspects to emphases summarized the solution based onplane and spatial problem, and they are compared according to the above researchresults.（3）Based on the above research results, the mechanical model for shield tunnel isestablished consideration of various influencing factors of shield construction.According to Mindlin elastic theory, the three-dimensional formula of stratumdeformation because of both the friction between the cutterhead and the soil and thegrouting pressure is deduced, and programmed the relevant calculation programs withMatlab6.5. The laws of stratum deformation caused by shield construction andinfluencing factors are researched with examples of engineering project. The analysisresults indicate that the calculation program is effective and reasonable, and the formulaof stratum deformation can reflect explicitly each influence factors.（4）On the basis of the case study of the shield tunnel of Nanchang Subway, thedynamic process of shield construction was simulated by using the finite differencesoftware (FDM) FLAC3D. Meanwhile, this paper discusses the laws of stratumdeformation caused by shield construction, and the results are compared and analyzedaccording to the site actual measurement data and the theoretical solution.The analysisresults indicate that the established three-dimensional mechanical model is reasonable, and the finite difference method may be used to predict the stratum deformation andanalyze the influencing factors. The formula of stratum deformation because of both thefriction between the cutterhead and the soil and the grouting pressure can get moreaccurate results, and it can be used to predict and calculate the stratum deformationcaused by shield construction in actual engineering. It has an important instruction todesign and construct of the shield tunnel.