Study on Design and Construction Safety of Open-cut Structure of Railway Tunnels in Shallow Water-bearing Soft Soils

Abstract

In the water-rich complex soft soil stratum, there are great difficulties in manual-excavated pile construction in cutting engineering, and it is very difficult to dig for forming piles in the water-rich sand stratum. There is water seepage and sand gushing, which leads to the risk of deformation and hole collapse, and the construction risk is extremely high. Based on the engineering example of changing the cutting of the portal section of the New Changqiangling Tunnel into an open cut tunnel during the construction of the second line of the Yangpingguan–Ankang Railway, and the stratum conditions and groundwater conditions revealed on-site, the paper introduces in detail the design and construction of cast-in-situ bored pile retaining open-cut structure which is used under the condition that the original design of cutting pile-sheet wall structure is difficult to be implemented, and it makes a detailed analysis of the advantages and disadvantages of cast-in-situ bored pile retaining open-cut structure with respect of structural safety, construction safety risk, construction quality control, construction cost, construction period, and operation and maintenance. The paper provides a very valuable reference for similar engineering design in the future as it solves the problem of the construction of deep cutting or shallow-buried tunnels in shallow-buried soils under site-controlled conditions, and at the same time greatly reduces the operation safety risk of the railway in deep cuttings.