Clay is a very important material widely used in geotechnical engineering. The mechanical
behaviours and engineering properties of clay, such as compressibility and shear strength, are
largely controlled by the microstructure of clay. In recent years, many studies have been
conducted to investigate the microstructure characteristics and micro-behaviour of different
clays by means of a variety of advanced techniques. However, the complexity of the whole
series of phenomena occurring at the micro-scale, when the clay is subjected to macroscopic
mechanics, makes the prediction of the clay macro-behaviour through the modelling of micro-behaviour a major challenge. Most of the existing studies only focus on the microstructure
characteristics of clays, and do not link these micro-features with the macroscopic mechanical
behaviour of clay.
The present research work systematically studies the intrinsic microstructure characteristics
of three different reconstituted clays and the main physical processes underlying the
mechanical response when they are subjected to compression and shearing, through
experimental laboratory testing in combination with detailed microstructure analysis of clay
specimens undergoing mechanical testing. With the aim to assess the microstructure evolution
and the corresponding micro-scale processes while the clay exhibits the given macro-mechanical behaviour, this thesis reveals the effect of clay microstructure on its macro-mechanical behaviour and establishes the constitutive relationship between clay microstructure
and macro-mechanical properties. The correspondence between the microstructure
characteristics of three different types of clays and their macro-mechanical behaviour presented
in this thesis can prompt a wider use of the constitutive models in practice, since it would
support the geotechnical engineer in the selection of the model and the parameter values most
appropriate for the clay involved in the design of interest.