Prediction of wetting-induced volume change behaviour of compacted unsaturated soils in the context of the MPK framework

Compacted unsaturated soils show distinct behavioural patterns when compared with their saturated counterparts, and these behavioural patterns become more and more complex when soil is subjected to wetting, such as swelling or collapse and loss of shear strength. Ignoring these possible complex behaviours of unsaturated soils coupled with varying climatic conditions can lead to inaccurate assessment of the performance of geotechnical structures. Therefore, the accurate prediction of the wetting-induced volume change behaviour of compacted unsaturated soils is a key step in understanding and modelling unsaturated soil behaviour. Of the different constitutive models introduced to date which can define the wetting-induced volume change behaviour of compacted unsaturated soils reasonably satisfactorily, the MPK framework for the volumetric constitutive behaviour of compacted unsaturated soils proposed by Kodikara (2012) has shown favourable results with its direct relationship to moisture variation. This approach provides a practical approach, where reliance is placed on the variations in the moisture or degree of saturation as input. From this perspective, this study evaluates the volumetric behaviour of compacted unsaturated soils due to various wetting state paths, and the results are compared with the predictions of the MPK framework. The results show that the MPK framework is capable of predicting wetting-induced volume change behaviour, including the wetting-induced yielding of compacted unsaturated soils.