Study On Loess Permeability Test In Xi’an

The seepage velocity of loess is an important content of soil water infiltration.Due to the particularity of loess structure,its permeability changes after water collapse,its permeability coefficient and seepage velocity change,and seepage velocity is an important index of permeability,so the permeability of loess can be studied by studying the change law of loess seepage velocity.In the process of water infiltration of loess,the driving force is mainly gravity potential,matrix potential and pressure potential,and the main influencing factors of seepage velocity are water head height,water content,surface tension,adsorption force and so on.In this paper,through the indoor water infiltration test,the relationship between the water head height,soil moisture and other factors is discussed,and the permeability characteristics of unsaturated loess moisture infiltration are analyzed from the change law of seepage velocity.This paper takes the loess in the north suburb of Xi’ an as the research object,and according to the seepage velocity problem of loess under different conditions,a test device has been developed.Through the infiltration test,the change law of the loess before and after the water immersion consolidation test is discussed.the analysis shows that the loess seepage velocity is directly related to the head height,and increases with the increase of the head height and decreases.Through the permeability test under different consolidation test conditions,the loess in the natural,dead weight and 200 kpa collapsible state,the weight collapse(saturation weight pressure less than 200 kpa)is the largest,200 kpa collapsible,followed by natural state is the smallest.Through the downward and upward infiltration test of unsaturated loess,it is found that,due to the effect of gravity potential,the downward seepage velocity of soil sample is larger than the upward seepage velocity of soil sample,and their difference is negatively related to dry density,correlation coefficient R = 0.930,and positive correlation with void ratio,correlation coefficient R = 0.919.