Study On Moisture Migration And Deformation Law Of Unsaturated Loess In Filling Region

The problems such as the change of underground water level and the rupture of pipeline that caused by the construction of loess fill make the loess under a cycle of humidity increasing and reducing for a long time.The moisture migration continuously infiltrates the foundation and changes the humidity state,then it results in the decrease of soil strenth,the deterioration of the engineering properties,and eventually leads to uneven settlement as well as deformation and destruction of the building,it makes great economic losses.Taking the unsaturated loess in Yanan fill area as the research object,this paper analyzed the water migration law of loess through the water migration test.The soil water characteristic curve was obtained by matrix suction test.On the basis of it,the variation equation of soil water content per unit volume was established to study the mechanism of water migration in unsaturated loess.The wetting deformation characteristics of compacted loess are analyzed with the moistening test.Finally,by ABAQUS,the moisture transfer model and the moist deformation model were established to carry out simulation of water transfer and moistening deformation of unsaturated loess,according to that,effects of dry density,moisture content and humidification cycle on moisture transfer and moisture content was investigated.The main conclusions are as follows:(1)Using the self-made water transfer system to carry out the moisture migration test in unsaturated loess.It was found that the rate of water migration decreased with the increase of the number of cycles,the increase of dry density and the decrease of initial moisture content.The moisture content of the final volume decreases with the increase of migration height,and the smaller the dry density and initial moisture content is,the larger the final volume water content is.(2)Measured by the matrix suction of soil by wet process and two humidity reduction-humidification cycle.It was found that the larger the dry density,the greater the suction of the soil sample matrix,and the higher the moisture content,the smaller the influence of dry density on the matric suction,and the lower the moisture content.Under the condition of wet and dry cycle,the soil water characteristic curve will form obvious hysteresis loop.And the influence of wetting and drying cycles on matrix suction is gradually weakened(3)Based on the results of water migration test and the loess soil water characteristic curve,the change equation of soil moisture content in unit volume soil was established.lt can be used to predict the final volume water content.(4)The wetting deformation coefficient of compacted loess increases with the decrease of the dry density and initial water content and the number of dry wet cycles.The collapsibility of loess is strong under high pressure.The influence of wetting and drying cycles on soil moisture and deformation characteristics is gradually weakened.Increasing dry density can effectively control the moistening deformation of compacted loess.