Using Retractable Baffle-Type Rectangular Pipe Jacking for the Construction of a Tunnel with a Large Cross-Section in a Complex Environment

Abstract

In this study, we propose baffle-type rectangular pipe jacking in the context of the world’s first shallow large-section rectangular pipe-jacking project under a high-speed railway line, with the aim of improving the utilization of underground urban space. We introduce the relevant method of construction as well as safety control technology for ongoing construction in the proximity of pipe jacking in a complex geological and structural environment, and propose techniques of optimization for the continued application of baffle-type rectangular pipe jacking in similar projects. The results showed the following: (1) the maximum value of the surface settlement as the pipe-jacking machine passed through it was 160 mm. But the maximum uplift, maximum settlement, and maximum relative settlement of the D-shape temporary beams were 6.31, −5.78, and 6.71 mm. (2) The theoretical mechanics-based calculations was used to derive the minimum safe distance required to form a stable microarch effect between the roofs of the pipes, and the recommended distance in the project considered in this study was 24 cm. (3) The results of assessments based on multiple measures showed that the proposed pipe-jacking method led to the successful completion of crossing work for high-speed rails that were in use. This means that it is feasible to use rectangular pipe jacking to pass through an operating high-speed rail in composite strata at a shallow depth. We also provide suggestions for applications of the retractable baffle-type rectangular pipe jacking in the future.