Study on safety analysis of raw water pipe under large section bored tunnel of shallow buried excavation

Abstract

In the process of urban construction and development, more and more large cross-section tunnels are excavated by shallow mining method for the improvement of traffic demand. The tunnel underpasses the important raw water pressure pipeline for water supply, which brings great challenges to pipeline operation and tunnel construction. In this study, the numerical finite element method is used to analyse the engineering case of the shallow buried large section tunnel under the raw water pipe. Using reasonable tunnel excavation construction method, this paper analyses the influence of large diameter primary water pipe of DN2700 and summarizes the relevant laws and control measures. It is find that when the temporary support of upper steps is removed during tunnel construction, the water pipe displacement will suddenly change. The surface settlement is about 1.9mm at most, and the vault settlement is about 3.5mm at most, which is mainly caused by the excavation of the upper steps and the removal of the temporary support of the upper steps and the arches. The calculation shows that through the DN2700 raw water pipe, the tunnel construction with reserved core soil method under IV grade surrounding rock can ensure the safety of raw water pipe and the stability of stratum. According to the measured data, the calculated results are in good agreement with the measured data.