Influence of Soil Fabric and Gradation on Excess Pore Water Pressure Development Based on Laboratory PWP Tester

Abstract The build-up of the excess pore water pressure (PWP) during shearing under constant total stresses can significantly influence the stability and performance of geotechnical structures, particularly in coarse grained soils under cyclic and dynamic loading conditions. This study investigates the role of soil fabric and granulometric properties in the generation of the excess PWP using a newly developed PWP Tester. Series of experiments were conducted on both natural and crushed sands with varying grain size distributions, grain shapes, and particle orientations. The results indicate that the resistance to the excess PWP build-up in natural soils increases with larger mean grain diameter and a reduced amount of fines, while crushed sand with narrower grain size distribution show a slight increase in resistance to the excess PWP development. Furthermore, the findings suggest that soil resistance to the excess PWP cannot be adequately captured by solely considering the relative density, and that the soil fabric plays an equally significant role. This study contributes to a deeper understanding of the soil behaviour under cyclic loading in undrained conditions, offering a simple and straightforward method for testing the soil tendency to the excess PWP evolution.