Large-scale experimental evaluation of soil saturation effect on behaviour of buried pipes under operational loads

Abstract

The behaviour of pipelines in unsaturated soil is fundamentally different from that of pipelines buried in dry or saturated soils. However, the effect of soil saturation on buried pipe behaviour has been overlooked in past research mainly due to the very limited large-scale experimental studies available. Most of the available studies on buried pipes in unsaturated soil are based on numerical modelling that analyses the pipe behaviour using a calibrated soil model developed on the basis of fundamental unsaturated soil characteristics. Investigations with such approaches may not be acceptable owing largely to unverified or complicated pipe–soil interactions and three-dimensional stress re-distributions. In this paper, the effect of soil saturation on buried pipe behaviour is investigated using a comprehensive large-scale experimental setup. A detailed methodology of large-scale testing, which was used to obtain pipe deformations as well as soil stresses with reference to a cast iron pipeline buried in low-plasticity clay under different soil saturation levels, is presented. The results obtained from large-scale experiments are compared with those of three-dimensional finite element analysis. Results produced in this paper reveal that the degree of water saturation of backfill soil can significantly affect the pipe deformation under internal and external loadings.