Analysis of influence of shield tunneling on overlying underground pipelines based on HSS model

Small strain stiffness properties of soil play an important role in correctly predicting the surrounding deformation of an underground excavation. Based on a case of analysis for overlying pipelines adjacent to the metro tunnel of Changzhou North Railway Station, a three-dimensional finite element model to analyze this typical problem is proposed. Small-strain of soil is considered to investigate the influence of shield tunneling on overlying underground pipelines. Based on Plaxis 3D, the hardening small-strain (HSS) constitutive model of soil is used in simulation analysis of the ground surface settlement and pipelines deformation. By comparing simulation results with the measured value, it shows that the actual deformation of engineering can be predicted more reasonably when the small strain stiffness of soil is considered in numerical analysis. After studying the influences on deformation characteristics of pipelines due to different burial depths, materials and the relative positions to the tunnel, it is found that the closer the pipeline is adjacent to the tunnel, the greater the influence is from the shield tunneling; and the increase of the stiffness ratio between the pipeline and surrounding soil can effectively reduce the settlement of the pipeline, but it increases the internal force of the pipeline.