Deformation Monitoring And Numerical Analysis Of Adjacent Complex Pipelines Caused By Deep Foundation Pit Excavation In Si Li He Road Station Of Hefei Metro

This paper chooses the Deep Foundation Pit Project of the Silihe Road subway station in Hefei as research background.According to on-site monitoring data and computer simulation from the finite differential software,it is possible to simplify the mathematical model,and simulate the deformation curve of the captured main on-site monitoring points via the feedback from the on-site construction.In addition,the simulation provides a feasible way to analyze and conclude the main part of the foundation pit and the deformation of its adjacent pipelines.Moreover,the deep analysis on the deformation of the pipelines crossing over the foundation pit can help formulate the deformation of adjacent pipelines.Apart from these,this paper also investigates the varied trends of the deformation of pipelines under different pipe spacing,pipe diameter,burial depth and wall thickness.The rules of the deformation are summarized as follow:(1)The diachronic change of the settlement of the sewage pipe and that of the rain pipe near the pit's monitoring point are almost the same.As the excavation position of the pit gets closer to the monitoring point,the excavation will have higher interference on the monitoring point.According to the simulation,the maximum vertical displacement is 0.22 L from the pit.The shape of the vertical displacement curve is “big in the middle and small at the ends”.And the changing rate of the vertical displacement is high at both ends of the pit.(2)The shape of the curve of the change of the crossing pipelines' vertical displacement depends on the contact between the pipelines in the pit and the soil.At both sides of the pit,the shape of the curve forms spoon-like grooves.It is important to pay extra attention to the position of the pipelines near the enclosure structure during pit excavation.(3)Practically,extra attention to the pipeline is required at 0.22 L away from the excavation position of the pit.Since there exists large difference between the elastic modulus and surrounding soil,the pipeline is not adaptive to the deformation of the soil.Thus,pipeline may significantly hinder the settlement of the soil.Under the same condition,the influence of the excavation of the pit to the pipelines is inversely proportional to their stiffness.When the pipe diameter is 0.5m,the influence of the excavation is minimum.When the pipe diameter is 0.5m and its wall thickness is 0.05 m,the influence of the excavation is minimum.The computational results are close to the monitoring data,and are within the limitation of control values.In this paper,it comprehensively analyzes the influence of the deep foundation pit to the deformation features of pipelines,and provides a reference to the on-site construction or similar projects.