Experimental Study On Mechanical Properties Of Clay Treated With Water Repellent

Soil water repellency is a physical phenomenon that water droplets on the soil surface can not or difficult to wet soil particles,and it is difficult for water to penetrate into the soil and wet the surface of soil particles.Most of the natural soil is hydrophilic soil,which is closely related to engineering safety issues,such as seepage damage,slope instability and so on.Because the soil has good hydrophilicity,water is easy to infiltrate into the soil,which leads to engineering safety problems.Compared with hydrophilic soil,hydrophilic soil can prevent water from entering soil particles.If hydrophilic soil is used to transform foundation and slope,some engineering safety problems caused by hydrophilic soil may be avoided and solved.Therefore,this thesis conducted a series of laboratory tests on water-repellent clay with water-repellent agent.The main research contents are as follows:(1)take drying and on outdoor air dry preparation of repelling water clay in two ways,after completion of preparation by dripping through time and degree of alcohol solution infiltration method for repelling water test,analysis of drying and air-dry the differences of two preparation ways,at the same time,compares two kinds of detection methods,study the test of a repelling water contact.The results show that the soil prepared by drying has stronger water repellency than the soil dried by natural air,because the temperature of the oven can make octadecylamine particles melt and adhere to the soil surface,forming a better water repellent layer.Both WDPT and MED can better describe the change trend of water repellency,and the two detection methods can complement each other.WDPT reflects the persistence of soil water repellent,while MED reflects the intensity of water repellent.(2)Prepare water repellent soils with different initial water contents for WDPT test to study the relationship between water repellent degree and water content.The maximum dry density,optimal water content and limit water content with the degree of water repulsion were studied by means of compaction test and limit water content test.The results showed that the water repellent degree of soil with different water repellent degree increased firstly and then decreased with the increase of water content.From hydrophilic to extremely repulsive,the maximum dry density increased by 8.9%and the optimal water content increased by 9.1%.Under the action of water repellent,the boundary water content of clay changes.With the increase of water repellent,the liquid limit water content decreases and the plastic water content increases(3)One-dimensional soil column infiltration test was designed by using Mahalanobis flask and soil column to study the soil infiltration law of hydrophilic clay and hydrorepulsive clay under the four designed soil bulk densities of 1.25g/cm~3,1.3g/cm~3,1.35g/cm~3 and1.4g/cm~3.The results show that soil bulk density has significant influence on the infiltration capacity of both hydrophilic and repulsive clays.The larger the soil bulk density is,the longer the time it takes to reach a certain infiltration height and accumulate infiltration amount.The profile water content decreases with the increase of soil depth,and decreases with the increase of bulk density at the same soil height.Under the same soil height and the same bulk density,the water content of the profile of hydrophobic clay is lower than that of hydrophilic clay.(4)Under three different water contents,direct shear tests were carried out on clay with different water repellent grades to analyze the variation rules of shear strength.The results show that under the same water content,the shear strength of soil increases with the increase of water repulsion degree.With the increase of water repulsion degree,the shear strength index of clay with severe water repulsion and extreme water repulsion does not increase significantly compared with that of clay with medium water repulsion degree,and the modification effect of clay with medium water repulsion degree is the best.The effect of water repellent on soil shear strength was more obvious under high water content,and the C value of medium water repellent clay under 15%,18%and 21%water content increased by 20%,28.6%and 61%,respectively,compared with that of hydrophilic soil.