The Use of Geotextiles and Related Materials in Reducing Stresses l on a Pipe Embedded in a weak Soil Under a Roadway Loads

Abstract

The behavior of a buried pipe in soil is a complex problem that must be addressed by applying the principles of soil-structure interaction. The goal pf this study is to stresses imposed on a cross-section of a pipe buried in weak soil and evaluate the effect of using geotextiles on the stress and displacement distributions at the cross-section using the finite element analysis method (FEM). Geotextiles were used to reinforce the backfill soil above the pipe. Three . types of pipe installations were studied. These are :

i) Trench bedding with compacted dense sand, ii) Trench bedding with plain concrete, iii) Embankment bedding with plain concrete.

The three types of pipe installations were studied with three heights of backfill over the pipe 2.0, 3.0 and 4.0m. The applied loads are determined according to the Egyptian Code of the loads for highways.

The commerical element package known as "LUSAS" (its full title, London University Stress Analysis System) was used in this •study. Two different soil models were suggested, the linear elastic model, and the non-linear elasto-plastic model. The soil-pipe and soil-reinforcement interfaces were modeled using an elasto-plastic interface materials based on Mohr-Coulomb criterion. For the interface between the soil and the pipe, two cases of interface friction were considered, frictionless slip (tan cp =0.001), and frictional slip (tan cp =0.25). Plain strain elements were used to represent the pipe, the soil and an interface element to model the soil-pipe interaction and the soil-reinforcement interaction. The reinforcement with geotextiles was modeled using thin-layer elements, which were allowed to support tensile forces only.