Theoretical Study on Surface Deformation Caused by Shield Tunneling along Curved Section in Saturated Soil
Due to the complex and ever-changing geological conditions of cities and the constraints of above-ground or underground buildings,shield tunnels along the curved section are commonly used in subway construction.Based on the initial value solution of semi-infinite saturated soil,considering the soil squeeze effect of unbalanced additional thrust on the shield excavation face,unbalanced friction of shield shell and spreading and softening effect of grouting at shield tail,and the soil loss caused by hoop filling of grouting pressure of the shield tail and over-excavation of curved shield,this paper deduced the theoretical calculation formula of the surface deformation caused by the shield tunnelling along the curved section in saturated clayey soil,and analyzed the law of the surface deformation and the influence of each param-eter.The calculated surface deformation is in line with the field measured law,which shows certain guidance of the pre-diction formula.Compared with conventional straight line shield tunneling,the construction of curved shield tunnels is more likely to cause great soil loss and asymmetric deformation of the surface.With the increase of the additional thrust on both sides of the excavation surface of curved shield and the difference between the inner and outer friction of the shield shell,the surface deformation also increases,and the maximum deformation value shifts towards the inner side of the curve.The offset of the axis and the maximum value are inversely proportional to the turning radius,while the diame-ter of the cutter head only affects the offset of the axis.
shield tunnelling in curved sectionsaturated soilconstruction factorsover-excavationasymmetric de-formation
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