Laboratory measurement of sensitivity of carbonate soils

Design of geotechnical structures such as piles and offshore pipelines requires knowledge of the soil’s sensitivity to account for the effect of remoulding on the soil’s strength. This effect of remoulding is particularly significant for soils exhibiting post-depositional structure, such as carbonate fine-grained soils. This paper investigates laboratory measurement of sensitivity using three different methods: fall cone, hand vane and mini T-bar penetrometer. Tests were conducted on two carbonate soils from offshore Western Australia, with different grain size distributions. Additional T-bar tests were performed on two reconstituted specimens of one of the soils that was consolidated from a slurry, to evaluate the influence of the method of reconstitution on the soil structure and sensitivity. The results for the more fine grained soil show that the fall cone and T-bar measurements of sensitivity are similar, whereas the hand vane yields much lower values, in particular for deeper samples; the sensitivity of reconstituted samples of this soil is approximately half that of the intact soil. The hand vane and fall cone data for the sandier soil investigated show a significant amount of scatter, with the average value of sensitivity being similar. The results are analysed in the light of existing frameworks for clays, investigating how soil sensitivity can be related to liquidity index and soil structure.