Bending Performance of F-Type Socket Joints for Rectangular Pipe Jacking Tunnels with Longitudinal Connectors

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.