Soil water retention behavior and microstructure evolution of lateritic soil in the suction range of 0–286.7 MPa

This paper presents an experimental investigation of the soil water retention curve (SWRC) and volume change curve over a large suction range (0–286.7 MPa), and microstructure evolution of Guilin lateritic soil under drying and wetting processes. The scanning electron microscopy results show that the reconstituted and compacted samples have very different microstructures. The soil samples compacted at optimum water content features flocculation of the colloids showing a low degree of particle orientation, while the reconstituted samples prepared from slurry produce dispersed arrangement of particles showing a high degree of particle orientation. The pore size distribution curves of reconstituted and compacted samples show the unimodal and bimodal distributions, leading to S-shaped and double S-shaped SWRCs, respectively. At the same initial density, the soils with a low degree of particle orientation (like compacted samples) exhibit less shrinkage than those with a high degree of particle orientation (like reconstituted samples). The mercury intrusion porosimetry test results show that the drying and wetting processes and initial density clearly affect the macropores of the compacted samples, while the micropores remain almost unchanged. For the reconstituted samples, the drying and wetting processes and initial density primarily affect the micropores.