Protection of Buried Flexible Pipes with a Geosynthetic: Experimental and Numerical Studies

Abstract

Geosynthetic materials have been used in a wide variety of ways to enhance the performance of buried pipes and conduits. Attenuation of surface loads to protect the pipe include methods such as induced trenches, soil enhancement for cyclic loading, and protection from penetration during construction or accidents. Geosynthetic materials have also been used to reinforce the in situ walls of trenches and to reinforce the backfill of buried pipes The previous studies have shown that geosynthetic materials can improve pipe performance by reducing strains and deflections. There appears to be an opportunity to improve the body of research in this area and to give practical guidance to engineers and designers. This study concentrates on pipes subjected to near surface loads, and includes full scale experimental studies of a steel reinforced high density polyethylene pipe (SRHDPE) in a trench condition with low cover. Two base course and backfill conditions were run with and without geogrid at the interface of the base course and in the trench. The experimental results showed that the geogrid reinforced base course can reduce deflections and strains in the pipe for the conditions tested. A non-linear three dimensional model of the static load experiments was generated to simulate the test conditions. The cap-yield soil model was used for the trench backfill and the geogrid and pipe were analyzed with orthotropic plates. With the calibrated models a parametric study was conducted to study the effects of various pipes based on bending stiffness and hoop stiffness. Results of the parametric study indicate that the most appreciable enhancement of geogrid reinforcement for pipes in near surface loads conditions, happens for pipes with low bending and hoop-stiffness.