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、集输和输送管道横贯加拿大。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、横向或组合荷载，这取决于管道相对于移动的地面的方向。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管材在内的聚乙烯软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)的设施进行一系列小直径MDPE管道的全尺寸测试，以开发一个数据库，并更好地了解管道在地面运动荷载下的行为。测试程序将包括以下内容：i)平面管道的轴向抗拔测试；ii)三通管道(分支管道)的轴向抗拔测试；以及iii)埋在松散和致密沙土中的管道的横向抗拔测试。将进行实验室单元测试，以找出砂土的岩土参数和本构模型，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，模拟从全尺寸管道测试中观察到的响应。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和决策，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 theusers. According to Natural Resources Canada, about 825,000 kilometers of oil and gas transmission, gatheringand 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 designguidelines for structural integrity assessment of pipelines in landslide areas were developed based on theobservations for rigid pipes, which may not be applicable to flexible pipes, such as Medium DensityPolyethylene (MDPE) pipes. However, flexible polyethylene pipes including MDPE pipes have been widelyused over the last few decades due to their various advantages. The design method for the assessment of theperformance of MDPE pipelines subjected to landslide loading is not well-developed. Full-scale tests and finiteelement (FE) modelling of MDPE are also very limited. In the proposed research, a set of full-scale tests ofsmall 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 fromground movements. The test program will consists of following: i) axial pullout testing of plane pipes; ii) axialpullout testing of pipes with Tee-junctions (branched pipes); and iii) lateral pullout testing for pipes, buried inloose and dense sand. Laboratory element testing will be conducted to find geotechnical parameters anddevelopment 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 fromthe 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 managementdecisions to ensure structural integrity of the pipeline and minimize the risk of pipeline failure.