Study On The Impact Of Dry Wet Cycle On Properties And Slope Stability Of Silty Sand

In this paper,the silty sand along the line of a expressway in Hebei Province is taken as the research target to study its strength change under the action of dry wet cycle and the cumulative plastic deformation of subgrade under the coupling action of dry wet cycle and dynamic load.The stability of subgrade slope is preliminarily analyzed by ABAQUS numerical simulation method.The main research contents are as follows:Firstly,the natural moisture content and density of the silt soil were tested,and the results were 7.42%and 1.72 g·cm^-3 respectively.The particle sieving test showed that the particles in the soil were mainly distributed above 0.075 mm,and the soil was judged to be silt soil.,the liquid limit is 26.5%and the plastic limit is 13.4%through the liquid-plastic limit test.The optimum moisture content of the silt soil is 12.2%and the maximum dry density is 1.86 g·cm3 through the compaction test;Secondly,silty sand samples with different moisture content and compactness are prepared,and indoor unconfined compressive strength tests are carried out on silty sand samples with different dry wet cycles.It is obtained that the unconfined compressive strength of soil changes with the number of dry wet cycles,which can be expressed by exponential function.Specifically,its strength shows a gradual decreasing trend with the increase of the number of dry wet cycles,After five dry wet cycles,the strength tends to be stable.The variation law of shear strength and its parameters of silty sand under the number of dry wet cycles is obtained by direct shear test.Similarly,the relationship between shear strength parameters and the number of dry wet cycles under different conditions is obtained by exponential function fitting;Thirdly,GDS dynamic triaxial is used to simulate the development law of cumulative plastic deformation of subgrade silty sand under different confining pressure,compactness,moisture content,dynamic stress amplitude and dry wet cycle times under dry wet cycle and dynamic load.It is found that the cumulative plastic strain of subgrade silty sand decreases with the increase of confining pressure,increases with the increase of dynamic stress amplitude,increases with the increase of compactness,and first decreases and then increases with the increase of moisture content,With the increase of the number of dry wet cycles,combined with relevant research,the variation curve of cumulative plastic strain of subgrade silty sand with vibration times can be better described by the mathematical model y=aN^b/（1+cN^b）,and the variation law of parameters under the influence of different factors can be obtained;Finally,the strength index of silty sand under dry wet cycle in chapter three is used to analyze the stability of embankment slope.Through ABAQUS finite element analysis software,the influence of different dry wet cycle times,compactness and moisture content on the stability of silty sand embankment slope is studied by strength reduction method.Numerical results show that the more dry-wetting cycles,the greater the moisture content,and the smaller the degree of compaction,the lower the safety factor of the slope.