The influence of shear thinning of Hydroxypropylmethylcellulose (HPMC) during dynamic centrifuge experiments

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4. The influence of shear thinning of Hydroxypropylmethylcellulose (HPMC) during dynamic centrifuge experiments

Hydroxypropylmethylcellulose (HPMC) is a versatile and affordable thickening agent widely used in the centrifuge for modelling dynamic processes. However, the rheological properties of HPMC solutions can vary based on the type of HPMC and the solution concentration. These variations potentially affect the model soil behaviour and must therefore be considered when designing centrifuge experiments. This study investigates the influence of shear thinning of HPMC solutions on the installation behaviour of a tubular pile, driven dynamically at an effective acceleration of 50g. Samples consist of GEBA sand, prepared at 80% relative density by dry pluviation and subsequently saturated using water, and a viscous fluid prepared using Methocel F4M. The experiments consist of a sequence of single-blow events that ultimately drive the pile down to 3 pile diameters embedment. The pile displacement and the spatial distribution of pore pressures in the sample are monitored for every blow. The results demonstrate the need for a viscous fluid to replicate true-to-nature saturated soil-structure interaction in the centrifuge. Additionally, it is shown that there exists a need to consider the shear-thinning behaviour of viscous fluid during the experimental design in relation to the anticipated shear rates during test execution. In broader terms, this work improves the existing centrifuge modelling toolkit to conduct fundamental research about dynamic processes at a reduced scale.

5th European Conference on Physical Modelling in Geotechnics (ECPMG2024)

Scaling principles and fundamentals