The rectangular pipe jack F-type socket joint is a flexible joint.The overloading of the surface and the uneven settlement of the foundation can easily cause the shear misalignment of the pipe joints,leading to tunnel engineering disasters.Based on the fact that the shear mechanical characteristics of the joint are still unclear in current research,the failure process,stiffness characteristics and influencing factors of the joint under shear load were studied by considering the structural characteristics of the F-type joint in the rectangular pipe jacking tunnel,combined with laboratory joint tests and ABAQUS three-dimensional precision numerical simulations.The results show that when the rectangular pipe jacking joint shear failure occurs,the loaded pipe joint presents a centrosymmetric failure.The shear force-shear displacement curves of joints in different strata are divided into three stages:the contact building stage,the steel ring warping stage and the weld cracking stage.The greater the foundation stiffness,the greater the relative shear stiffness.The stiffness coefficient increases with the increase of the thickness or the width of the steel bushing.With the increases of the width and thickness of the steel bushing,the shear resistance of the joint increases,while the increase range remains limited.The stiffness coefficient of the steel bushing at the yield stage is about 60％-70％of the elastic stage.
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