Analytical Analysis Of Earth Pressure Balance Shield Tunnel Face Stability And Application In Engineering

The Shield Method is defined as an engineering technology which has a highdegree of mechanization and automation. The most essential requirement of shieldmethod is the face stability because of the high security and efficiency. The key ofresearching on the face stability is to estimate the range of the support pressure andalso it is necessary to restrict ground settlement. The research work is presented asfollows:（1）Firstly, the minimum limit pressure of three-dimensional wedge modelbased on the limit equilibrium method is derived to calculate the failure pressure andthe failure angle. Calculation results is verified with the conclusion of classic test、limit analysis method、numerical method in different ratio between depth and diameter.According to the observation data, the influence of the support pressure to the surfacedeformation is analyzed.（2）The limit failure pressure analytical of the simplified two-dimension modeland three-dimension are derived to verify with the construction of the model andanalyze the sensitivity of the influence factors.（3）Then the concept of TSF（tunnel stability factor）is proposed to study therelationship between limit support pressure and ground deformation. The index ofTSF are calculated based on large amounts of investigation data and ground surfacesettlement information of subway in Beijing. The mathematical expression of TSFrelated to support pressure is obtained by non-linear curve fitting according to thedifferent stability factor. Then based on the settlement data analysis, the relationshipbetween TSF and settlement is analysized.The index of TSF is presented to indicate a certain quantitative relationshipbetween the face support and the ground settlement, which provides the reference for the engineering practice and a new guide for the face stability analysis. However,because of the limit number of projects, the index needs a further verified with similarproject.