Volume change behaviour of an unsaturated compacted loess under thermo-hydro-mechanical loads

The volume change behaviour of an unsaturated compacted loess under thermo-hydro-mechanical loads is comprehensively investigated in this experimental research. A new temperature/suction-controlled triaxial apparatus with triple cells was developed. Temperature- and suction-controlled isotropic tests, heating-cooling tests with isotropic net stress and suction control and drying-wetting tests with isotropic net stress and temperature control were conducted on an unsaturated compacted loess from Shaanxi, China. Experimental results show that compressibility indices remain unchanged at various temperatures, but show different variation trends with changes in suction. Both suction hardening and thermal softening were observed. Irreversible volumetric contraction is induced in the compacted loess upon heating-cooling path and becomes more significant at higher isotropic net stresses and higher suctions. Lower over-consolidation ratio prior to heating results in greater irreversible contraction in loess samples. Water-holding capacity of loess samples decreases upon heating, but it is independent of the stress level. The hydraulic hysteresis of samples has no significant change with temperature changes. Slight shrinkage occurs during drying process in loess samples, and collapse can be observed in wetting process. Heating has limited effect on the drying shrinkage of loess samples but induces more distinctive wetting collapse.