Influence Analysis On Adjacent Pipeline Displacement By Deep Pit Excavation

Influence analysis on adjacent pipeline displacement by deep pit excavation has been ahot topic of the pit environmental engineering.It’s difficult to meet the demand of protectingthe pipeline with the existing theory of pit designing. Recently, many scholars and engineersput forward based pit designing and deforming methods to reinforce the protection toward thesurroundings.This text is based on one civil air defense engineering in Xiangtan. Because the pipelinecover densely around and too close to the pit, people should focus on how to assure the safetyof adjacent pipeline during construction. This article adopt a method of spot actualmeasurement combined with numerical value simulation, profoundly researching on adjacentpipeline displacement by deep pit excavation， the main context and conclusion arefollowing：At first, it works out a scheme of pipeline monitoring, and monitors the horizontal orvertical displacement during construction. The result shows that, pipeline horizontaldisplacement increase by the depth of excavating，it tend to steadiness with the exerting of theprestress and the pouring bedplate concrete of the pit；While the pattern in which the verticaldisplacement of pipeline change with the depth of excavating is: from rebound to sink.Second, adopting plane strain analytical method focus on the research of the influence ofstep excavation, prestress, steel pipe pile size, embedded depth of steel pipe pile, groundoverload, the analyzing result indicates that, the displacement of pipelines can be reducedeffectively within a certain range (≤120kn) prestress; the influence extent of the increase ofsteel pipe pile size on vertical displacement surpass that on horizontal displacement; thehorizontal displacement of the pipeline increases linearly with the increase of the groundoverload.Third, adopting three dimensional numerical analytical method focus on researching theinfluence of step excavation, steel pipe pile spacing, distance of pipeline from the pit,different pipeline depth, diameter of pipeline on the displacement. Numerical simulation ofpipe with beam elements, and has been taken into account of the weight of the fluid in thepipe and the interaction between soil, retaining structures, the result shows, that the horizontaland vertical displacement of the pipeline distribute on a parabola along longitudinal directionof the pit, the maximum horizontal and vertical displacement lies on the central symmetry flat;the horizontal displacement increased by the space between steel pipe pile, while verticaldisplacement reduces with the increase of the space; farther the pipeline is from the pit, lessthe displacement will be, for the extent of influence on horizontal displacement mainly focus on the twice excavating depth behind the retaining structures; longer the diameter of the pipeis, wider the horizontal displacement will be, while shorter the vertical displacement will be.What’s more, with the increase of the diameter, the morph of the pipeline along itslongitudinal direction becomes gentler.