Discrete Element Modelling of uplift of rigid pipes deeply buried in dense sand

Abstract

This paper presents a numerical methodology based on the Discrete Element Method developed for the efficient modelling of kinematic granular soil-pipe interaction at large deformations. The methodology is based on a robust Bayesian procedure for calibrating micromechanical contact parameters using standard triaxial compression tests, does not rely on the back-analysis of physical model experiments, and produces accurate “blind” predictions of independent experimental measurements. The latter is demonstrated by extensively validating DEM models against measurements obtained from direct shear tests on sand performed during this study and published measurements from 1-g physical model experiments of uplift of rigid pipes buried in dense sand. In addition, we introduce different approaches that allow efficient modelling of deeply buried pipes, and we employ the methodology to investigate how the reaction from sand to rigid pipe uplift varies as the pipe embedment depth increases. Detailed numerical predictions provide insights into the “flow-around” failure mechanism that develops around the deeply buried pipes and on the existence of a critical embedment depth, beyond which the normalised reaction does not further increase with increasing pipe embedment. The outcomes of this study are applicable to the stress analysis of deeply buried pipes in practice and to the modelling of a variety of problems relevant to rigid objects buried deeply in granular soil.