Modelling the Collapse of Metastable Loess Soils

Hydrocollapse of loess continues to cause major geotechnical problems the world over. Modelling the behaviour of these soils is still in its early stages. Computer models are often used to model saturated soil behaviour but for collapsing unsaturated loess soils such models are difficult to implement due to the complex nature of collapse. One method that will help overcome difficulties such as the role of clay bonding or soil fabric, is to consider collapse from a particle packing perspective, rather than as a soil suction problem. The way the particles pack together decides whether a soil is metastable or not. Using this philosophy, work is currently being conducted to develop a constitutive model to be incorporated in CRISP90 in order to analyse the behaviour of collapsing loess soils. This paper will discuss the development of this model and the methods used to validate it, which include the use of an artificial loess soil manufactured in the laboratory. This model material has been shown to reproduce loess behaviour very well and enables a full range of reproducible and repeatable tests to be conducted.