Experimental assessment of sampling disturbance in calcareous silt

Abstract

A small-scale physical modelling program using particle image velocimetry and digital image correlation techniques was designed to obtain a refined understanding of the disturbance experienced by calcareous silt during tube sampling. The influence of the sampler wall thickness (diameter-to-thickness ratio, B/t) and the tube penetration rate were evaluated by estimating displacement and strain fields around the tube sampler. The results indicate that sampling with a thin tube leads to a relatively narrow undisturbed zone located at the centre of the tube, with a width slightly smaller than the tube radius. Opposite to what is suggested for soft clays, tube sampling tends to densify the calcareous silt. This aspect has an important influence on the assessment of sample quality in calcareous silt for offshore and onshore projects.