Laboratory tests to evaluate mechanical properties and performance of various flexible pipes

This study presents the experimental results for seven different tests carried out on high-density polyethylene (HDPE), PVC, and metal pipes with medium-size diameters. The main objective of the experimental program is to evaluate and characterize, under laboratory conditions, the performance and mechanical properties of the various flexible pipes considered in the study. The diameters of the pipes studied are 36 in. (914 mm) and 48 in. (1,219 mm). The laboratory tests conducted are the simple-beam test, parallel-plate test, flattening test, curved-beam test, joint-integrity test, and tensile test, as well as an environmental stress-cracking test. The results of the tests are presented in terms of load-deflection relations, load versus longitudinal and transverse strains, failure modes, and pipe stiffness. The test results indicate that HDPE and PVC pipes show good performance compared with metal pipes. In addition, the experimental results for flexible pipes meet AASHTO specifications. The HDPE and PVC pipes tested according to the ASTM and AASHTO Standards show pipe stiffness values higher than the minimum specified by the standards. The pipe stiffness values of the HDPE specimens based on the curved-beam test are two to three times greater than those based on the parallel-plate test. It was found that for a given vertical deflection, the HDPE pipe stiffness substantially increased with an increase of loading rate.