Effects Of Wetting-drying And Freezingthawing Cycles On Microstructure And Engineering Properties Of Expansive Soil In Seasonal Frozen Area

Due to the composition of hydrophilic minerals,expansive soils are prone to swell or shrink with the change of humidity.Most studies used to focus on the single effect of wetting-drying or freezing-thawing.But under the long-term changes of wettingdrying and freezing-thawing cycles,expansive soils are always in an unstable condition,and this has a negatively impact on the long-term stability of engineering construction.Therefore,experiments were conducted to research the engineering properties of expansive soils,in order to study the coupled effects of wetting-drying and freezingthawing cycles.In this paper,the expansive soils are taken from a channel slope in Daqing,Heilongjiang Province,China.The temperature and humidity controlled container is used on the pretest processing to simulated the cyclic wetting-drying and freezingthawing environment of the seasonal frozen area.(1)The different pore size distribution and microscopy images of expansive soils under cyclic environmental effects were obtained by MIP and SEM tests.(2)The stress-strain behavior and shear strength parameters of expansive soils were obtained by triaxial consolidated undrained sheer tests.(3)The soil-water characteristic curves(SWCCs)of expansive soils were obtained by using the axis-translation technique and vapor equilibrium method.(4)By shrinkage tests,the evolution of volume,void ratio and saturation of expansive soils under cyclic environmental effects are obtained.With these results,It is revealed the development of strength,deformation and soil-water characteristic within different cyclic environmental effects,and the reasons for the evolution are explained by microstructure studies.This paper provides a reference for engineering construction.