Study of the relationship between hydro-mechanical soil behavior and microstructure of a structured soil

Structured soils, such as residual laterites or volcanic ashes, abound in tropical regions. The hydro-mechanical behavior of these soils is clearly related to their structure. New techniques based on microstructural studies constitute a powerful tool for investigating these soils. This work presents an experimental investigation that documents the relationships between the microstructure and the mechanical behavior of these soils. This study focuses on the microstructural behavior of Brasilia clay, a structured, highly porous tropical soil (n>50%) with a bimodal pore size distribution. The microstructure was investigated using pore size distribution analyses of different structural states and void ratios. The mercury intrusion porosimetry (MIP) technique was used to explore the pore size distribution of samples in various conditions, i.e., natural, compacted, slurry or consolidated states. Modeling of the pore size distribution curves was performed using the bimodal van Genuchten curve, which permits the linking of the pore size distribution curves (PSD) to the water retention curve. We observed that loading and compacting did not affect the micro-pores of this soil, and we conclude that the changes occurred entirely within the macro-pores.