Research on the disturbance effects of large-diameter shield tunneling side-crossing on existing pile foundations in composite strata
The construction of urban tunnels is trending towards larger diameters,making it in-evitable for tunnels to laterally pass through the pile foundations of various building types in composite strata.However,most existing theories focus on small-diameter tunnels in homoge-neous strata,with limited attention given to the disturbance effects of large-diameter shield tunnels passing through pile foundations in composite strata.To address this gap,we consider the characteristics of large-diameter shields and divide the soil displacement caused by tunnel excavation in homogeneous strata into elastic and elastoplastic stages,based on the theory of circular hole contraction.We then derive formulas for calculating the stress,displacement,and radius of the plastic zone induced by large-diameter shield tunnel excavation,accounting for the continuous variation of calculation points.Additionally,the composite stratum model is treated as the combined effect of a homogeneous stratum model and the additional interface forces gen-erated by stratigraphic layering.Using a two-stage analysis method,we propose a calculation method for the horizontal displacement and bending moment of pile foundations induced by tunnel excavation in composite strata.Numerical simulation inversion provides a formula for determining the additional interface stresses.The validity of the proposed method is confirmed through a comparison of existing methods and numerical results.Finally,this method is applied to the Chunfeng Tunnel project,where the influence of the stratum interface position on the deformation and internal forces of pile foundations during tunnel passage is analyzed.The results demonstrate that the proposed method effectively accounts for stratigraphic layering and accurately reflects displacement changes due to lithological variations;in soft-me-dium-hard composite strata,tunnel deformation is significantly influenced by the position of the interface.
large-diameter shieldadditional interface forcepilecomposite stratadisplace-mentbending moment
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