Effect of strain rate on pore pressure evolution and effective stress path of soft soil under different stress history conditions

Abstract

Soft marine soils are highly plastic fine-grained soils and known for their high compressibility, large water content and low shear strength behaviour. The previous research on soft soils is restricted to stress–strain response under conventional loading conditions with and without its treatment. The effect of strain rate on pore pressure evolution and effective stress path of soft soil under different stress history conditions has not been explored. In the current research, an extensive experimental research has been performed on Kanjurmarg soft marine soil to evaluate its pore pressure evolution, effective stress path, obliquity and effective stress ratio at different strain rates and varying stress history conditions. A wide range of strain rate, 0.005% per min to 5% per min, was used to perform the CU triaxial tests on soft soil. Such large strain rates are used to analyse the behaviour of soil under various field conditions such as rapid excavation, rapid application of surcharge, aircraft wheel loading on runways, fast installation process of pile and projectile penetration. The effect of stress history on soft soil was also explored for OCR values of 1, 2, 5, 10 at different strain rates. The soil was also tested at different confining pressures at varying strain rates to evaluate the combined effect of strain rate and confining pressure.