Construction Technology for Composite Structure of Rectangular Pipe-Jacking and T-shaped Beam-Plate and Backing Counterforce Wall with Corner Braces

For the unconventional working condition where the starting well of the irregularly-shaped rectangular pipe is located on one side or both sides without a permanent structure serving as the rear counterforce wall, in order to solve the technical problems of the traditional counterforce wall structure, such as large engineering volume, poor anti-shear performance, and difficult removal, therefore, the research innovatively proposes a construction technology for a cast-in-place reinforced concrete rear retaining wall using a T-shaped beam slab and corner braces. The core mechanical innovation of this technology lies in converting the force system, adding diagonal corner braces connecting the bottom plate and the T-shaped beams, optimizing the simple-supported force model of the traditional rear counterforce wall into a continuous beam force model, thereby reconstructing the force transmission path and significantly enhancing the overall stiffness and anti-shear capacity of the structure. The research was carried out based on the East Extension Project of Guangzhou Rail Transit Line 3. The results show that through the rigid connection of the T-shaped beams and the bottom plate and the supporting point effect of the corner braces, the thrust force is transformed from a point load to a surface load and diffused to the bottom plate, reducing the calculation span and maximum bending moment of the main load-bearing components effectively. While meeting the requirements of the raft slab for anti-shear and shear resistance, this technology saves approximately 40% of the cost and shortens the construction period by 30% compared to the traditional wall-supported counterforce wall; compared with the T-shaped beam plate + ox leg steel support scheme, the construction period is shortened by 66%, and it has the advantages of simpler procedures, better force transmission, and higher reliability. The engineering monitoring data indicate that no structural cracks occur on the rear counter-force wall under maximum thrust load, and the maximum displacement at the top of the wall was only 0.71 mm, ensuring the stability of the rear support during the pipe-jacking process and the accuracy of the pipe axis effectively.