| As a shortcut city traffic, the subway has gained rapid development in the21stcentury. Areas along the MTR became the first choice of real estate development, mo-re and more excavation engineerings were built over the subway tunnel which has be-en exist. Pit excavation will cause a certain range of soil under excavation face emergeunloading rebound，forcing the subway tunnel to float up. To ensure the safety of thesubway, chosing reasonable design and construction techniques to control the deform-ation of subway tunnel become an issue that must be solved. Taking pit excavation innorth square of Tianjin Western Railway Station as background, this paper research t-he effect of pit excavation on Metro Tunnel and pit.The main contents as follows：1. Research the strength and deformation characteristics of the soil underunloading state and establish a constitutive model of soil to simulate stress-strainrelationship under the unloading state.2. According to the size of the excavation and the distance from the lower part ofthe tunnel, provide the oversimplified method of deformation calculation of tunnel.3. With finite element analysis software ABAQUS, analysis the effects ofdifferent measures which can reduce the deformation of the tunnel,such as shorten theexposed time, reduction of the excavation area, upliftpile and soil improvement；Providing numerical simulation analysis method to more realistic situations,Effectively predict the deformation of the tunnel and additional stress under pitexcavation.4. Establish empirical formula to estimate the springback of basement and tunnel;Calibrated using field data to improve the simplified calculation method and providepractical method to detect amount of deformation of the tunnel. |
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