Investigation of pull-out behaviour of small diameter medium density polyethylene pipes

管道在现代社会中扮演着重要的角色，它将液体和气体从源头输送到**用户。根据加拿大自然资源公司的数据，大约825,000公里的石油和天然气输送、收集和分配管道横贯加拿大。这些管道中的许多都经过易发生滑坡的地区。**滑坡引起的土壤移动可能会对管道造成纵向、横向或组合载荷**，具体取决于管道相对于移动地面的方向。现有的滑坡地区管道结构完整性评估设计指南是基于对刚性管道的**观察而制定的，这可能不适用于软管，如中密度聚乙烯(MDPE)管道。然而，在过去的几十年里，包括MDPE管在内的柔性聚乙烯管由于其各种优点而得到了广泛的应用。MDPE管道在滑坡荷载作用下的**性能评估设计方法尚不成熟。MDPE的全尺寸试验和有限元(FE)建模也非常有限。在拟议的研究中，将利用纽芬兰纪念大学**(MUN)的设施对**小口径MDPE管道进行一系列全尺寸测试，以开发一个数据库，并更好地了解管道在**地面运动载荷下的行为。测试程序将包括以下内容：i)平面管道的轴向抗拔测试；ii)T形接头管道(分支管道)的轴向抗拔测试；以及iii)埋在**松散和致密沙子中的管道的横向抗拔测试。将进行实验室单元测试，以确定岩土参数和**砂土本构模型的建立以及MDPE管道材料的应变率相关行为。**将使用ABAQUS有限元软件开发有限元建模技术，以模拟**全尺寸管道测试的观测响应。这项研究的结果将对加拿大管道行业有用，**使他们能够评估不稳定地面上的管道状况，从而做出更有效的管理**决策，以确保管道的结构完整性，并将管道故障的风险降至最低。

Pipelines play an important role in modern society through transporting liquids and gases from the source to the**users. According to Natural Resources Canada, about 825,000 kilometers of oil and gas transmission, gathering**and distribution pipelines traverse Canada. Many of these pipelines pass through the areas prone to landslides.**Soil movement due to landslides may cause longitudinal, transverse or combined loads on the pipelines,**depending upon the orientation of the pipeline with respect to the moving ground. The existing design**guidelines for structural integrity assessment of pipelines in landslide areas were developed based on the**observations for rigid pipes, which may not be applicable to flexible pipes, such as Medium Density**Polyethylene (MDPE) pipes. However, flexible polyethylene pipes including MDPE pipes have been widely**used over the last few decades due to their various advantages. The design method for the assessment of the**performance of MDPE pipelines subjected to landslide loading is not well-developed. Full-scale tests and finite**element (FE) modelling of MDPE are also very limited. In the proposed research, a set of full-scale tests of**small diameter MDPE pipe will be conducted using the facility at Memorial University of Newfoundland**(MUN) to develop a database and an improved understanding on the behaviour of pipes under the loads from**ground movements. The test program will consists of following: i) axial pullout testing of plane pipes; ii) axial**pullout testing of pipes with Tee-junctions (branched pipes); and iii) lateral pullout testing for pipes, buried in**loose and dense sand. Laboratory element testing will be conducted to find geotechnical parameters and**development of constitutive models for sand and the strain rate dependent behavior of MDPE pipe materials.**FE modelling techniques will be developed using Abaqus FE software to simulate the observed response from**the full-scale pipe tests. The findings from this research will be useful to the Canadian pipeline industry,**enabling them to assess pipeline conditions in unstable ground and thus to make more effective management**decisions to ensure structural integrity of the pipeline and minimize the risk of pipeline failure.