Influence of Backfill Soil Saturation on the Structural Response of Buried Pipes

Abstract

The structural design of new buried pipes and the calculation of the remaining service life of in-service buried pipes are usually conducted assuming that the backfill soil is at the optimum moisture content using the unsaturated soil parameters published by Boscardin et al. (1990). These unsaturated soil parameters are also implemented in the CANDE software, which is a standard software developed for designing buried culverts/pipes. However, intense rainfall seasons, floods, or water table rise due to changes in local drainage conditions may change the state of the backfill soil from unsaturated to saturated conditions. The purpose of this paper is to study the robustness of using the unsaturated soil parameters in the design of new buried pipes and the calculation of the remaining strength of in-service buried pipes by comparing the response of buried pipes for unsaturated and saturated backfill conditions using three-dimensional finite element analysis. Cast iron, concrete, and unplasticized polyvinyl chloride pipes have been considered to address the aim of the study. The results have shown that the soil saturation increases the stresses of the pipe wall, displacement of the pipe, and the soil pressure applied on the pipe. Hence, there is a need to understand and consider the unsaturated/saturated soil mechanics in the design and the analysis of buried pipes/culverts.