Influence of developed Benoto piling on deformation of adjacent high-speed railway subgrade in soft soil area

A new constructed high-speed railway line between Lianyungang and Zhenjiang with pile-plank supported subgrade will be emerged into the existing high-speed railway line between Shanghai and Nanjing. To meet the requirements of height limitation of the high-speed railway catenary, a new type of height-limited piling equipment and corresponding piling technologies for developed Benoto piles adjacent to high-speed railways were proposed in this project. To reveal the influence of Benoto piling on the deformation of surrounding strata and adjacent high-speed railway subgrade, this paper adopted field tests combined with numerical analysis. In the field tests, displacement monitoring devices were used to monitor the horizontal deformation of strata during piling. Then, Benoto pile-strata-subgrade finite element model was established for calculating the deformation of high-speed railway subgrade during group piles construction. The construction sequence of group piles, construction safety distance and auxiliary deformation control measures were discussed based on this numerical model. The results indicated that the developed Benoto piling generally leads to transverse extrusion deformation of surrounding strata. In each process of piling, the steel casing construction induces the most significant disturbance to surrounding strata. The strata, especially those within the length of steel casing, show obvious horizontal displacement. The construction safety distance of Benoto piling adjacent to high-speed railway can be determined by field tests and numerical simulations. When the distance between the piling region and the existing subgrade cannot meet the critical construction safety distance, the steel sheet piles can assist to control subgrade deformation. The deformation control effect of steel sheet piles on subgrade is positively related to the pile length and negatively related to the distance from the piling region. The results can provide suggestions for the deformation control of existing high-speed railway to ensure its safe operation. © 2023, Central South University Press. All rights reserved.