A simplified analysis for deformation behavior of buried pipelines considering disturbance effects of underground excavation in soft clays

Underground excavation, such as tunneling and deep foundation pit, will no doubt induce the soil disturbance and have result in uneven settlements of adjacent buried pipelines which adversely affect and even damage the structures. In order to explicitly point out construction interaction mechanism and rapidly predict the structure mechanical behavior, a simplified displacement-controlled two-stage method and stress-controlled two-stage method are presented for determining the deformation behavior of pipeline structures caused by underground excavation in soil clays. According to tunneling project, the free soil deformation calculated by the displacement-controlled boundary element solution is used to estimate the soil disturbance effects of underground excavation. The oval-shaped ground deformation pattern is imposed to the tunnel opening to consider the nonuniform convergence characters. According to foundation pit project, the free soil stress based on the Mindlin solution is used to predict the soil disturbance effects of underground excavation. The situations that the excavation unloading center is not acting on the pipeline axis and that the excavation boundary and pipeline axis are formed with an arbitrary angle can fully be considered. Then, the free soil deformation and free soil stress are imposed onto existing pipelines to analyze the interaction mechanics between the disturbance soil and buried structures. The accuracy of proposed method is demonstrated with existing calculation results, centrifuge model tests, and site investigation data. In addition, the parametric analyses for the deformation influence factors of existing tunnel induced by foundation pit excavation, including the horizontal distance between the excavation boundary and tunnel axis, the tunnel buried depth, the tunnel bending stiffness, and the crossing angle between the excavation boundary and tunnel axis, are presented to demonstrate the performance of the proposed method. The results indicate that the proposed method can be used to estimate the mechanical behavior of buried pipelines considering disturbance effects of underground excavation with higher precision.