Monitoring-Based Assessment of the Construction Influence of Benoto Pile on Adjacent High-Speed Railway Bridge: Case Study

With the rapid expansion of the high-speed railway (HSR) network in China, some new lines must be constructed near or across existing HSRs, which will likely have an effect on the operational safety of the HSRs. The existing HSR bridges are highly sensitive to the construction influence of the adjacent piles, and a small displacement of HSR bridges may cause high-speed trains to derail, with disastrous consequences. Consequently, pile construction adjacent to HSRs should be accompanied by an appropriate method to mitigate its detrimental effects on HSRs. The Benoto method is considered to be environmentally friendly and economical because of its fast construction efficiency, low slurry discharge, and no risk of shaft necking. Few studies have been done investigating the influence of Benoto pile construction on adjacent HSR bridges. This study fully explores the construction influence of Benoto piles on neighboring HSR bridges. Specifically, the Nanjing S3 Metro Line project in China serves as the test bed, and a comprehensive field monitoring system was installed to measure soil displacement and stress as well as HSR bridge pier displacement. Several observations can be made on the basis of this study: (1)the variation in soil stress and lateral movements is slight when the distance between the pile and the soil exceeds 18m; (2)the settlement of the surrounding soil is especially obvious when the steel casing is pulled out; and (3)the settlement of soil at the bridge site and the horizontal displacements and inclination angles of existing piers do not exceed the corresponding warning, which indicates the safe operational condition of the adjacent HSR during the construction of Benoto piles. The findings of this work may provide useful guidance for the design and construction of piles adjacent to in-service HSRs.