Mechanics of compression in the reconstituted and intact shale with a transitional mode of behaviour

Abstract

• Mechanics of compression in shale investigated in detail. • Fabrics are heterogeneous with particle aggregation and few inter clusters voids. • Strong transitional behaviour in both reconstituted and intact shale. • Increase in strength and stiffness due to bonding and fabric in shale. Due to the important nature of shale as a suitable host materials for engineering applications and its characteristics in association with other materials, a detailed knowledge about the behaviour of shale is very crucial. Since geological and geotechnical problems associated with design and construction of engineering structures could be analysed using oedometer tests data, therefore studying the behaviour of geomaterials in compression is vital. In order to achieve this, an extensive series of oedometer tests were carried out on the reconstituted and intact shale samples from different depths. Apart from this, index and physical properties, compositional, fabric and mineralogical analyses were also investigated. The fabrics of the reconstituted and the intact samples are characterized by aggregation of particles forming continuous clusters with few inter-clusters pores. No unique normal compression lines and there is transitional behaviour in the intact sample and the degree of transitional behaviour is robust even in the reconstituted samples. The behaviour of the shale samples depends on the initial state. The compression parameters are low and the maximum resistance to yielding is medium to high. Although the intrinsic properties are non-unique, the degree of enhanced resistance in compression has been recognised and discussed. The overall implication is that the non-uniqueness of shale normal compression lines should be considered when characterizing their properties but provided good intact samples are tested, the engineering design parameters will still be valid for the shale in-situ.