Consequence of drying on the compression behaviour of soft clay

Abstract

The soft clay is widely distributed in the nearshore and offshore areas in China. The sensitivity to drying and wetting raises serious concerns about the durability of structures exposed to climatic stress changes. More research is urgently needed to improve our understanding of the response of soft clay to drying. To this aim, soil shrinkage and compression tests on natural and reconstituted samples were performed, supported by mercury intrusion porosimetry and scanning electron microscopy tests. The initial soil structure is found to be the key factor in the response of drying. The pore size distributions of natural and reconstituted samples exhibit the bimodal and unimodal features, respectively. Drying starts affecting the macro-structure, without changing the micro-structure, until a threshold void ratio is reached, below which desaturation occurs of inner-pores. The threshold void ratio discriminating between inter and inner porosity was consistently found from the test data provided by this study. Above this threshold, the drying decreases the compressibility which dominated by the macrostructure response. Below this threshold, the modification of structure occurred within inner-pores, in turn dramatically increases the apparent yield stress and reduces both the primary and secondary compressibility. Pore refinements occurs upon drying, which is characterized by the progressive changes in the PSD and the arrangements of particles and aggregates, the natural and reconstituted samples reach the similar pore structure and compressibility eventually.