Influence of Foundation Pit Groups' Excavation on the Deformation Characteristics of Adjacent Railway Subgrade and Protection Measures

This study employs a series of finite element models and field monitoring data to systematically investigate the deformation characteristics and protective measures of railway subgrades adjacent to excavation sites for groups of foundation pits. A baseline model with a single foundation pit is established based on a project to erect a viaduct in an area with soft soil, and the model is verified by field monitoring data. The effects of the number of foundation pits, the distance between adjacent foundation pits, and the distance between a foundation pit and an adjacent railway subgrade are studied. The results show that increasing the number of foundation pits, reducing the distance between adjacent foundation pits and decreasing the distance between a foundation pit and the railway subgrade lead to excessive settlement and horizontal deformation of the subgrade. Three kinds of subgrade protection measures, namely, increasing the thickness of the retaining structure, setting isolation piles, and adding grouting reinforcement, are proposed and analysed. Increasing the thickness of the retaining structure significantly reduced the horizontal displacement and settlement of the subgrade.