Numerical Analysis of the Impact of Overcut on the Soil-Pipe Interaction in Pipejacking
管推進工法 ； 曲線推進 ； 數值分析 ； 滑材 ； 超挖 ； 地盤改良 ； pipe-jacking ； curved pipe-jacking ； numerical analysis ； lubricant ； overcut ； grouting
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近年來都會區為普及地下污水管道，正普遍地進行地下管線的埋設工程。因人口與建物分佈密集，明挖覆蓋法(cut and cover method)已逐漸被淘汰，取而代之的管推進工法(pipe jacking method)漸成主流。於地下開挖施工中免不了會遭遇超挖、擠壓、卡鑽以及周邊存在有施工中或已完工之鄰近工程結構物造成互制影響等狀況而需待解決。另外於推進過程，常於管體與孔洞間灌注滑材，減低管土之間的摩擦力，進而降低推進力，增加推進效率，避免因推進力過大造成管材破裂的發生。前人針對管推進工法研究模擬滑材一般都採用改變摩擦係數來模擬不同介面性質，並未真實考量滑材材料性質。此外對於超挖造成開挖面大於切削面盤之效應，與管推進路線鄰近地下建物所造成之互制影響關係並未做詳細之探討。因此本研究針對直曲線管推進受滑材性質、超挖範圍、地盤改良範圍與鄰近建物間距等因素進行數值分析。 本研究使用ABAQUS有限元素軟體建立水平向管推進數值模型，探討於直曲線推進過程，灌注滑材性質之差異與超挖範圍之大小對於鄰近土體與管材之互制行為分析。此外，加以考量當直線管推進路線鄰近地下既有管線、河渠以及地下基礎等條件下，其滑材性質、鄰近間距和地盤改良範圍對於土體與既有結構物之影響性分析作一詳細探討。 研究結果發現:1.滑材可明顯降低管土間互制行為，降低土壤應力。2.隨著擴張超挖範圍，開挖面周邊土壤受擾動影響程度增大，於開挖面上土壤應力解壓情形越顯著，擾動變位亦增加。3.管推進對於鄰近建物影響範圍最大約為三倍管徑，隨著既有建物不同而有所差異。4.當鄰近間距過短而進行地盤改良之模擬結果顯示，推進管周圍土體應力皆增加，而變位大致呈現減少之趨勢，建物鄰近推管端之應力變位也顯示降低之情形，說明確實達到穩固土層與保護建物之目的。
For the popularity of underground sewer, underground pipelines are more and more common buried in Taiwan in recent years. Due to the dense population and buildings, the cut and cover method has gradually been replaced by no-dig methods, and the pipe jacking method becomes one of the major no-dig methods in Taiwan. It is inevitable that we need to resolve the problems of the interaction effects caused by overcut, squeezed, sticking and the surrounding existent constructions during the installation of pipelines. Furthermore, during the process of pipe jacking, it often perfuses lubricant in the hole to reduce propulsion as well as friction between the pipe and soil, to increase propulsive efficiency. And avoid the pipe rupture due to excessive jacking force. The previous studies focus on pipe jacking method which considers the different lubricant by change the coefficient of friction to simulate the interface properties. But, they didn’t have a detailed discussion on the influence of overcut and the relationship of the interaction caused by the route close to adjacents buildings. Hence, this study focus on pipe jacking consider lubricant, overcut, grouting, and the influence of adjacent buildings by numerical analyses. In this study the finite element software ABAQUS is used for the numerical analysis of horizontal pipe jacking, including the simulation of the influence of lubricant property and the range of overcut on the soil-pipe interaction. In addition, a detailed discussion was performed on the impact of lubricant, adjacent spacing, area of grouting between soil and existing structures. For the study of the influence of adjacent buildings, this study considers the conditions of straight pipe jacking route close to existing underground pipelines, open channel and underground infrastructure. The results show that: 1. lubricant can obviously reduce the stress surrounding the pipe; 2. the disturbing of the pipejacking on the surrounding soil was increased as the overcut increasing, the soil stress was decreased but the disturbance on the excavation face will be increased; 3. the maximum distance of influence of adjacent buildings is about three times the diameter of the pipelines; 4. for the case of jackng the pipe near buildings, simulation results show, soil stress was increased around the pipe, and soil displacement was decreased by the grouting. And it is certainly worth noting that grouting can stable the ground and protect the building.
工程學 > 土木與建築工程