THE INFLUENCE OF SURROUNDING SOIL ON FLEXIBLE PIPE PERFORMANCE

The response of 160-mm-diameter, shallowly buried, unplasticized polyvinylchloride (uPVC) pipes to surface loading has been investigated in full-scale tests. Standard installation and loading conditions were used to study the influence of the surrounding soil below, beside, and above the pipe on pipe performance. The type of soil used to surround the pipes was found to have a considerable influence on pipe behavior. Various uncompacted granular materials provided good support, whereas uncompacted silty clay and silty sand did not. Compaction of the surrounding soil had a variable influence wholly dependent on soil type. Silty clay performed well only when thoroughly compacted in thin layers. Light compaction of a broadly graded granular soil improved performance slightly, whereas uniform gravel is generally considered to be unresponsive to compaction. The use of a thin bedding layer was shown to be beneficial in reducing pipe deformation, whereas a thicker bedding layer was shown to be less beneficial. The problems of measuring pertinent soil properties on site for fill selection are discussed and assessment of two empirical methods is made.