Evaluation of Circumferential Strain of Low Stiffness Buried Pipe Subjected to Both Internal Pressure and External Load

Abstract

Model tests are conducted to investigate the behavior of low stiffness pipes such as thin Polyvinyl chloride (PVC) pipes (VU) subjected to internal pressure and external load. The test results show that the deformation of VU subjected to external load is induced by not only moment but also axial load. In the case of VU pipe buried in medium dense sand (relative density 61%), the ratio of axial strain to bending strain is 40% when the surface load is 150 kPa. The axial strains of the pipes buried in the sands of different densities (relative density 61% and 39%) by external load are almost same, which means that axial strain is insensitive to soil stiffness. The axial strain of VU buried in medium dense sand subjected to internal pressure and 150 kPa of surface load is above 10% smaller than that to internal pressure and 0 kPa of surface load. This indicates that the axial strain is reduced as the surface load is large. Moreover, results of tests used with duct pipe that is thinner than VU show that these tendencies become more prominent for lower stiffness pipe.