Experimental investigation into the effects of voids on the response of buried flexible pipes subjected to incrementally increasing cyclic loading

Abstract

In this study, large-scale fully instrumented laboratory tests were conducted to investigate the behaviour of buried flexible high-density polyethylene (HDPE) pipes, in sand beds with and without voids subjected to incrementally increasing cyclic loading. Voids with a predetermined size were created at one side of the springlines of the pipes, which were buried at variable depths, H, of 1.5, 2.0 and 2.5 times the diameter of the pipe, D. Results showed that increasing the pipe burial depth, H/D, contributed to decreasing the settlement of the footing, deformation of the pipe crown and invert, lateral displacement of the spring-line, and the stress and strain generated along the pipe crown and invert. Void presence led to a significant increase in the footing settlement, which ranged from 3 % up to 18 %, according to H/D. Furthermore, void presence led to a sharp increase in the crown, invert, and spring-line settlements, which ranged from 34 % to 52 %, 10 %–12.5 %, and 13 %–38 %, respectively. Increasing pipe burial depth was found to be highly effective in protecting buried pipes, minimising inevitable consequences of the presence of voids. However, this was combined with an increase in the pressure at the pipe spring-line that led to a positive horizontal support at the pipe’s spring-lines resulting in reducing pipe deformation.