Experimental study of deformation and strength characteristics of Jingmen unsaturated expansive soil

The comparative analysis on the diversity of water retention characteristics between Jingmen intact and lime-treated expansive soils is investigated by the pressure plate tests.The deformation and strength characteristics of unsaturated and saturated intact,lime-treated and compacted expansive soils are studied by unsaturated triaxial tests.The results show that the air-entry value decreases markedly,the residual water content increases notably and the slope between the two characteristic points is more gradual,which demonstrates that the water stability is improved after the lime-treated.Secondly,the types of stress-strain relation curves of intact and lime-treated expansive soils are all strain softening under the unsaturated and saturated conditions,the grade of strain softening is more gradual with increasing net confining pressure,and the peak stress increases with decreasing water content.The types of saturated and unsaturated compacted expansive soils are strain hardening and strain softening respectively,but the grade of strain softening of unsaturated compacted expansive soils is more gradual than the other soils.And far more important,the values of shear strength parameters are improved significantly after the lime-treated,lime-treated expansive soil can maintain the higher values of strength parameters and fairly stable mechanical properties even under the saturated condition.By contrast,the strength of intact and compacted expansive soils is very sensitive to wetting effect.