Research on Excavation Surface Stability of Shield Tunnel under Jiuweigang River
Based on the project of Nantong subway shield underpassing Jiuweigang River,the three-dimensional wedge theory of shield tunnel excavation face stability in heterogeneous and isotropic strata is established.Considering the effect of groundw-ater,the calculation formula of the minimum supporting stress when the soil of shield tunnel excavation face in silty sand is in the active failure state(subsidence)and the calculation formula of the maximum supporting stress when the soil is in the pas-sive failure state(uplift)are derived.The corresponding calculation program is compiled to calculate the shield support stress underpassing 200 and 323 rings of Jiuweigang River Tunnel.Compared with the empirical formula,the calculation results of the three-dimensional wedge theory is more consistent with the actual excavation earth pressure value.Furthermore,the effects of cohesion and internal friction angle on support stress with different ratio of tunnel depth to diameter(H/D)are discussed.The results show that the minimum support stress decreases with the increase of cohesion and internal friction angle,and the value of H/D has a great influence on the minimum support stress,and the minimum support stress increases significantly with the increase of H/D,which can provide a reliable theoretical basis for tunnel engineering design.
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维普
