In unsaturated soils, pores are filled partly by water and partly by air. Unsaturated soils occur naturally (as superficial ground above the water table) or in manmade structures (as compacted earth in infrastructure embankments, underground nuclear waste repositories and flood defences). Unsaturated soil mechanics has experienced significant advances during recent years, instigated by the use of compacted earth as sustainable building material and by the pressing need of the construction industry to improve techniques for management and appraisal of earth structures.
Seminal contributions to unsaturated soil mechanics have been made over the past two decades but the current state-of-the-art is still unable to provide an accurate understanding of pre-failure behaviour in compacted soils, which is crucial to ensure long-term serviceability and cost-effective maintenance of earth structures. Mechanical non-linerarity and dependency of small-strain stiffness, as well as damping, on stress history are important properties not properly described by existing constitutive models. Understanding the response of compacted soils at small strains is not only central to applications in engineering dynamics, such as predicting ground motion during earthquakes or next to high-speed railways, but also to the analysis of earth structures under static loads of service.
The proposed project will contribute to fill such gaps of knowledge by pursuing two intertwined lines of investigations. Firstly, it will undertake a wide-ranging programme of triaxial and resonant column tests on unsaturated clayey silt samples compacted both in the laboratory and in-situ following standard procedures to ensure comparable material fabrics. Secondly, it will formulate a constitutive model capable of describing mechanical behaviour from small to large strains and will highlight advantages and limitations of such model when reproducing the behaviour of soils compacted both in the laboratory and in-situ.