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The construction disturbance caused by pipe jacking is an index that must be strictly controlled in the project. With the wide application of curved pipe jacking in urban underground construction, predicting its ground surface settlement characteristics has become an increasingly important research topic. Based on finite element numerical simulation, a three-dimensional model of curved pipe jacking was established to simulate the construction stage. Compared with the straight pipe jacking, the normal component of jacking force is set in the outer tunnel of the curved pipe jacking to simulate the extrusion of the outer soil caused by the corner of the pipe joint, and the surface settlement characteristics of the curved pipe jacking are explored by changing the pressure value. The research results show that the surface settlement of the curved pipe jacking conforms to the normal distribution as a whole. Compared with the linear pipe jacking, the surface settlement is not symmetrical about the design axis of the tunnel. With the increase of the pressure outside the tunnel, the maximum settlement value of the surface and the difference between the two sides of the axis increase. Compared with the Peck formula, the width of the settling tank of the curved pipe jacking is larger, the convergence rate outside the width of the settling tank is slower, and the settlement trend is more in line with the Verruijt formula. The calculation formula is modified by axis offset distance and ovalization coefficient and modified formula can better reflect the measured engineering data. The research results can provide guidance and reference for the prediction and control of surface settlement of curved pipe jacking.

A thorough understanding of the effects induced by continuous curved pipe jacking on adjacent underground facilities is paramount for ensuring both safety and operational efficiency during construction. This study posits a three-stage analytical framework designed to calculate the displacement of existing objects resulting from sequential vertical curved rectangular pipe jacking. The methodology involves the following stages: first, the stresses at the object surface must be derived based on classical Mindlin’s solutions; second, the displacements at arbitrary points of the object must be determined using the Winkler foundation model, wherein soil–object interactions are modeled as elastic springs to transform displacements into normal and shear forces; and third, the rigid-body displacement and rotation of objects, caused by aggregate forces, must be calculated by kinematic analysis. The validity of the proposed method is confirmed through comparison with a reduced-scale experimental test, and a parametric study discussing the influence of key factors, including Poisson’s ratio and object geometry, is presented.

Utilizing data from the Gongbei Tunnel's curved steel pipe section within the Hong Kong–Zhuhai–Macao Bridge, the accuracy of jacking force calculation methods in circular curve pipe jacking was examined. Then, an ABAQUS-based finite element model considering the grouting effect and the pipe-soil contact range is established, and the calculation of the jacking force is carried out. Upon comparing the results with measured jacking force data, it is evident that the JMTA formula, Shanghai code formula, and Shimada formula exhibit a descending order of accuracy in calculating jacking force values. Notably, the lower limit calculation value of the Shimada formula, which accounts for 1/3 pipe-soil contact surface, closely approximates the measured value. Numerical simulations reveal that a 1/3 contact state simulates the jacking force, gradually approaching the 1/2 contact state. In the grouting state, the measured jacking force aligns closely with the 1/2 contact state in the early stages of simulating the jacking force; conversely, during later stages when jacking stabilizes, the measured jacking force more closely resembles the 1/3 contact state. Consequently, the predicted jacking force of the numerical model considering the pipe-soil contact state is closer to the actual jacking force, which can provide a valuable guidance for the calculation of jacking force under similar working conditions.

Joint deflection during curved pipe jacking in power tunnels poses a significant risk of structural failure due to the resulting eccentric and diagonal loading on the pipes. This study investigated the axial stress and strain characteristics of reinforced-concrete pipes under varying joint deflection angles and jacking forces, using a combined approach of experimental model testing and finite element method (FEM) numerical simulations. The experimental setup replicated curved pipe jacking conditions, allowing for the measurement of strains and deformation under controlled loading. Numerical simulations, validated against experimental data, provided detailed insights into the stress distribution patterns. The results revealed distinct stress states in different pipe sections. The pipe closest to the jacking force (3# pipe) experienced eccentric loading, leading to localized stress concentrations and inelastic strain on the inner wall at the point of eccentricity, indicating vulnerability to compressive failure. The middle pipe section (2# pipe) underwent complex diagonal loading, resulting in the development of inelastic strain on both the inner and outer walls at specific orientations, highlighting a risk of both compressive and shear failure modes. The study also demonstrated that the magnitude of the axial jacking force and the degree of joint deflection significantly influence the stress distribution and the extent of inelastic strain. These findings provide important information for optimizing the design and construction of curved pipe jacking projects in power tunnels. The identified failure mechanisms and the influence of key parameters on pipe behavior can inform strategies to mitigate the risk of structural failure, improve the resilience of pipe systems, and enhance the overall safety and reliability of underground power tunnel infrastructure.