To solve the problems of insufficient stiffness and poor integrity of traditional F-type socket joints, steel screw connections are set along the longitudinal direction between rectangular pipe jacking joints. However, the mechanical properties of F-type socket joints with steel screw connections have not been fully investigated, and the influence of the coefficient of subgrade reaction has not been considered. In this work, through model tests and numerical simulations of F-type socket joints with steel screws under different coefficients of subgrade reaction, the influence of steel screws on the deformation and damage characteristics of F-type socket joints is discussed, and the bending mechanical response of F-type socket joints under different coefficients of subgrade reaction is analyzed. Compared with traditional F-type socket joints, the use of steel screw connections can reduce the risk of steel ring warping and cross-sectional deformation of the joints and improve the stiffness and load-carrying capacity of the joints. However, the use of steel screw connections exacerbates damage to the chamfered parts of the jack joints. With an increase in the coefficient of subgrade reaction, the benefit of the steel screw on the joint stiffness gradually decreases. For every 0.5-fold increase in the coefficient of subgrade reaction, the effect of the steel screw on the joint bending load-carrying capacity of the joint is reduced by approximately 23%. The failure mode of joints containing steel screws is mainly the crushing of concrete in the compression zone, and the penetration cracks extend from the joint to the bottom of the pipe section. The higher the jacking force is, the higher the load-carrying capacity of the joint and the better the bending resistance.

Joints are the weakest part of rectangular pipe jacking tunnels, and the structural form of the joint is closely related to its bending resistance. In this work, the F-type socket joint of a rectangular pipe jacking tunnel is selected as the object of study. The bending mechanical properties of the joints connected by steel screws and those connected by bent bolts are compared via a three-point bending test. The results show that the two longitudinal connection joints have similar bending stiffnesses. Compared with the bent bolt connection joint, the steel screw connection joint has better toughness, and the load at which the joint enters the plastic stage and the bearing capacity are increased by 0.47 times and 1.02 times, respectively. The failure modes of the joints connected by steel screw connections and those connected by bent bolts are crushing of the concrete of the top plate and cracking of the concrete above the screw holes, respectively. When a bent bolt connection is used, the reinforcement at the screw hole should be locally strengthened, or ultrahigh-performance concrete (UHPC) should be used at the screw hole to improve the load-bearing capacity of the joint.