Study on the deformation of existing tunnel under the combined effect of pit excavation and dewatering based on the Kerr foundation model

Abstract

There is a significant progression towards the trend of significant depth and extensive scale in foundation pit construction, where the excavation range is large and dewatering measures are usually required. To overcome the shortcomings associated with the complexity of the 3D numerical analysis model and the long period of on-site measurement in existing studies, a two-stage analysis method is proposed to consider the impacts on existing tunnels under the combined effects of pit excavation and dewatering. The first step involves calculating the additional stress imposed on the existing tunnel under the construction of pit bottom, pit side, and dewatering. Secondly, a differential equation describing the deformation effects on the existing tunnel is established based on the Kerr foundation model. Finally, the control equation is solved using the Galerkin method. Three engineering cases with different locations and tunnel parameters are selected to validate the proposed method. The effects of various factors on the deformation of the existing tunnel under the influence of pit excavation and dewatering are analyzed. Subsequently, an orthogonal experiment is designed to analyze the significant factors influencing the deformation of the existing tunnel and their prioritization, and an optimal parameter combination for controlling the existing tunnel deformation is obtained.