Buried polyethylene pipes used in gas distribution systems can experience excessive wall strain when exposed to ground movement that can affect the performance of the pipes in service. This paper presents full-scale laboratory tests performed to investigate the responses of medium-density polyethylene (MDPE) gas-distribution pipes in dense sand when subjected to axial ground movement. Pipes buried in sand in a large test box were pulled at the rates of 0.5 mm/min, 1 mm/min, and 2 mm/min to simulate relative ground movement in the longitudinal direction. The test facility was instrumented to measure pulling force, pipe wall strain, and soil stress. The measured pullout force was significantly higher than predicted using the equations recommended in current design guidelines, which is attributed to the increase of normal stress on the pipe wall by shear-induced dilation of interface soil. The cavity expansion theory was successfully applied to calculate the normal stress increase. The distribution of measured strains was nonlinear along the pipe length. Assuming a parabolic distribution of the strains, simplified equations were developed to calculate pullout resistance and pipe wall strain from the relative ground displacement. The developed method reasonably predicted the pipe strain measured during the tests.

中文翻译：

---

受轴向位移影响的密砂中聚乙烯管道的应变评估

用于配气系统的埋地聚乙烯管道在暴露于地面运动时可能会承受过大的壁应力，这会影响管道的使用性能。本文介绍了为研究中密度聚乙烯 (MDPE) 配气管在密砂中受到轴向地面运动时的响应而进行的全面实验室测试。以 0.5 毫米/分钟、1 毫米/分钟和 2 毫米/分钟的速度拉动大型试验箱中埋在沙子中的管道，以模拟纵向的相对地面运动。测试设备用于测量拉力、管壁应变和土壤应力。测得的拔出力明显高于使用当前设计指南中推荐的方程式预测的拔出力，这是由于界面土的剪切引起的膨胀增加了管壁上的正应力。空腔膨胀理论成功地应用于计算法向应力增量。测得的应变沿管道长度呈非线性分布。假设应变呈抛物线分布，开发了简化的方程式以根据相对地面位移计算拔出阻力和管壁应变。开发的方法合理地预测了测试期间测量的管道应变。开发了简化的方程式来根据相对地面位移计算拔出阻力和管壁应变。开发的方法合理地预测了测试期间测量的管道应变。开发了简化的方程式来根据相对地面位移计算拔出阻力和管壁应变。开发的方法合理地预测了测试期间测量的管道应变。