Experimental study of trench effect on lateral failure mechanisms around the pipeline buried in clay

Abstract

Pipelines are usually trenched and backfilled using the pre-excavated soil as cost-effective protection against the environmental, constructional, and operational loads. The design of buried pipelines for potential lateral displacements caused by ground movements is a challenging aspect that is usually simplified by assuming a uniform soil stratum. However, the remoulded backfilling material and its lower stiffness compared with the native ground can significantly affect the soil failure mechanisms and the mobilized lateral soil resistance. In this study, a qualitative experimental assessment was conducted to investigate the lateral pipeline-backfill-trench interaction effect on soil failure mechanisms and the resultant lateral soil resistance in shallow and deep burial conditions. Particle image velocimetry (PIV) was used to observe the interactive soil displacements directly. The partially drained condition was adopted to magnify the pipeline-backfill-trench interaction effects. It was observed that the interactive effects of pipeline, backfill, and trench precede their individual shear strengths and reduce the ultimate soil resistance. Also, the study revealed the significance of the pipeline/trenchbed interaction in the mobilization of the lateral soil resistance and several other mechanisms not yet addressed in the literature. As a result, several new research avenues were identified, and the ground was prepared for proposing cost-effective solutions to improve the prediction of the lateral response of buried pipelines in the near future.