الفهرس 
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Abstract
The goal of this study is to evaluate the effect of using geotextiles on the stress and displacement distributions at the crosssection of a pipe buried in weak soil 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. Two different soil models were suggested, the linear elastic model, and the nonlinear elastoplastic model. The soilpipe and soilreinforcement interfaces were modeled using an elastoplastic interface materials based on MohrCoulomb criterion. For the interface between the soil and the pipe, two cases of interface friction were considered, frictionless slip (tan (Sz ?(B0.001), and frictional slip (tan (Sz ?(B0.25). Plain strain elements were used to represent the pipe, the soil and an interface element to model the soilpipe interaction and the soilreinforcement interaction. The reinforcement with geotextiles was modeled using thinlayer elements, which were allowed to support tensile forces only. A nonlinear finite element comparative study of reinforced and unreinforced soilpipe interaction was conducted. Many trails of different locations of geotextiles were carried out to find the best location of geotextiles, which gave the highest reduction of stress and displacement of the crosssection of the pipe. This was carried out for the three cases of study at the different heights of backfill. Typical results of this study showed that the relative decrease in the tensile stress in the pipe using reinforcement was about 30%. Reinforcement reduced the magnitude of displacements.