Construction Techniques for and Cost Analysis of Secant Piles for the Pre-Reinforcement of Tunnels in Sand Strata

Considering that the Shangbai tunnel on the Datong-Xi′an passenger dedicated railway line, 1 717 m in total length, is at risk of sand gushing caused by construction in the dry, fine siltstone strata of different thicknesses, the construction technique of using a secant pile for tunnel pre-reinforcement is proposed based on research performed on the physical and mechanical properties of this strata. A relevant scheme comparison and some relevant issues, such as the construction technology process and construction difficulties regarding the secant pile for pre-reinforcement, are discussed in light of the absence of a clear professional quota standard for this technique, especially regarding the unit price of its construction cost.