Experimental study of hydromechanical behaviour of a compacted lateritic sandy lean clay

Lateritic clay is widely distributed in tropical areas and used extensively for foundation materials. Compared to other soils, it is rich in iron and aluminum oxides (sesquioxides), which enhance the formation of soil aggregates. The principal objective of this study is to investigate the hydromechanical behaviour of a lateritic sandy lean clay. All specimens were compacted at the same condition and then wetted to a predefined suction (0, 50, 150 kPa). Suction-controlled isotropic compression and shear tests were carried out. Moreover, soil microstructures at various suctions were determined using the mercury intrusion porosimetry (MIP) and scanning electron microscope (SEM) techniques. The compressibility of the lateritic clay decreased by about 50% as suction decreased from 150 to 0 kPa. This is mainly because as the suction decreased to 0 kPa, the sizes of interaggregate pores decreased, as revealed by MIP data. During shearing, the critical state friction angle appeared to be independent of suction. The contribution of suction to the apparent cohesion is unexpectedly low, likely because the interaggregate pores have a low degree of saturation and the contribution of the water meniscus on shear strength is very low.