自來水管線含水力學試驗與非線性側推之研究

Abstract

本研究首先針對自來水接續管線進行試驗研究，選擇延性鑄鐵管(DIP)中，K型接頭、A型接頭管，以及延性鑄鐵平口管(多用於制水閥前後，與用戶水表接續，或者淨水廠內各單元間之接續)，進行耐震性能試驗，受測管材之標稱管徑統一取為DN400；試驗過程中以油壓致動器逐步施加位移，強制受測管材在加壓滿水的條件下，產生超出規範所容許的接頭伸縮量或彎折角，以研究其破壞機制與耐震能耐。 經由管材耐震試驗，可知K型接頭之水密性良好，但不具防脫功能 ; A型接頭延性鑄鐵管(試體承口端為A型接頭十字管，插口端為D2K直管)水密性不良且不具防脫功能，在軸拉力或彎矩作用下，接頭十分容易鬆脫，耐震性能極差；延性鑄鐵平口管(試體由兩支單突緣短管對接)屬剛性接頭，軸拉與轉角的變形容量均極低，接頭界面之橡膠墊圈彈性不足，稍有張力或加壓後卸載即會漏水。基於以上研究成果，證實A型接頭延性鑄鐵管十分容易鬆脫，耐震性能極差，既有管線應加速汰換；平口管則變形容量極低，實不宜單獨作為輸配水管線之使用，若用於制水閥前後，或是淨水廠各單元間接續使用，則宜加強此類接頭之密合度檢查。 第二部分為進行分段管線非線性側推分析，在執行側推分析之前，必須先配置接頭的非線性塑鉸參數，前人研究中利用材料參數與實驗分析的結果建立管體的軸力、壓力、彎矩非線性塑鉸，而本研究則是利用試驗結果與非線性挫屈分析的比對結果，建立接頭的軸力、壓力、彎矩非線性塑鉸。總合上述兩部分的結果，利用案例分析探討了延性鑄鐵管DN400mm的管體受平移斷層之行為，考慮容許錯動量以及管線破壞模式，在接頭控制破壞模式下可以發現容許錯動量有減少的趨勢。

關鍵字：地下自來水管線、管線試驗、局部挫屈、非線性鉸、地層錯動、側推分析。

This study has firstly conducted seismic testing of the DIPs. Three joint types, namely K-type-joint、A-type-joint and flange joint, were selected for the testing. Full and pressurized pipe specimens were tested under tension, compression and bending load, separately. The deformation capacity and failure mechanism of each pipe specimen were investigated experimentally. According to the test results, K-type-joint DIPs are high tightness of water but easily disengaged under either axial tension or bending load ; A-type-joint DIPs are low tightness of water and easily disengaged under either axial tension or bending load ; flange-joint DIPs, as rigid joints, have very low tensile and flexural deformation capacity; leakage may occur as a result of poor elasticity of the gaskets. The following recommendations can be made according to the finding : Due to the fact of poor seismic performance, existing A-type-joint DIPs should be replaced as soon as possible; owing to the poor deformation capacity, flange-joint DIPs should not be used for water transmission and distribution; regarding the other usages, the water tightness of flange-joint DIPs should be regularly inspected. Before carrying out nonlinear pushover analysis of pipelines, K-type-joint nonlinear plastic hinges must be set. In the early literature, material parameter and the analysis of ABAQUS are used to set the tube axial and moment plastic hinges. In this study, the K-type-joint axial and moment plastic hinges are set by combining the results of the tests and analysis. According to the results of nonlinear pushover analysis, the allowable fault displacement and failure model of pipes under the strike-slip fault are investigated. Under the failure mode controlled by joint of the pipes, the allowable fault displacement tends to decrease when compared with the continuous pipeline without joints.

Keywords: water pipelines tests, pushover analysis, plastic hinges, DIP, K-type-joint, A-type-joint, flange-joint, local buckling