Soil Flow Mechanisms around Cone Penetrometer in Layered Clay – PIV Analysis in Centrifuge

Cone penetrometer test is widely used for in-situ site investigations and for establishing direct penetrometer to foundation or anchor design correlations. This paper focuses on the soil flow mechanisms during the continuous penetration of a cone penetrometer in layered clays. A series of centrifuge tests was conducted with the cone penetrating through soft-stiff, stiff-soft, soft-stiff-soft, and stiff-soft-stiff clay profiles. Particle image velocimetry allowed accurate resolution of the soil flow mechanism around the cone where a half cone model was penetrated into layered clays against a transparent window. The observed soil movement was compared with both previous observations for pile/cone, and with movement from shallow strain path method (SSPM). The comparison with SSPM results showed that SSPM can provide reasonable evaluations on maximum lateral and vertical displacements even though the upheave movement can be overestimated. The effect of soil layering on the failure mechanisms was studied extensively by exploring soil flow mechanisms and soil displacement paths at various distances from the advancing cone centreline and soil layer interface. The reported characteristics of cone penetration in layered soils provided in-depth understanding of cone penetration responses that will lead to the development of mechanism-based theoretical model for cone penetration in layered fine-grained soils.