Recent developments in modelling of soil-pipe interaction

With Dr. George Kouretzis of Priority Research Centre for Geotechnical Science and Engineering, The University of Newcastle, Australia. Buried pipelines crossing seismic faults, subsidence zones, or areas susceptible to liquefaction-induced lateral spreading are designed to accommodate differential ground movements without developing excessive bending and axial strains, frequently by implementing special mitigation measures. This requires performing nonlinear numerical analyses with general purpose or specialised finite element software, where the soil reaction developing on the pipe as result of differential movements is modelled by means of elastoplastic Winkler springs. The purpose of this talk is to present recent experimental measurements and numerical estimates of the developing soil reaction on the pipe, as function of relative soil-pipe movement, used as input in beam-on-nonlinear-Winkler spring analysis models. The presentation will focus on scenarios not covered by existing guidelines, such as deeply buried pipes and pipes laid in trenches excavated in stiff soil. Details will be provided on experimental methods developed to physically model relative soil-pipe movements, while carefully controlling the mechanical properties of the backfill, as well as visualisation techniques applied to shed light on the mechanisms of pipe-backfill interaction. Advanced numerical tools are also employed to analyse cases of complex pipe-backfill-trench geometry, and quantify the resistance provided by native stiff soil on pipes backfilled with loose sand. The presentation will conclude with a discussion on the limitations of numerical tools for modelling soil-pipe interaction, and recommendations for estimating soil spring parameters in practice. Hosted by University of Liverpool, sponsored by Optum CE.