Experimental Study On Soil Mechanical Properties Improvement Of Medium Expansive Soil Slope

In this paper,the medium expansive soil in Shannan New area of Huainan City is taken as the research object,and cement and soil-cement are respectively used as the main amendments to the expansive soil.Two improvement methods are adopted to improve the expansive soil with cement and replace expansive soil with soil-cement,and the expansion characteristics and direct shear characteristics of expansive soil are studied by laboratory tests.The basic physical tests of expansive soil,the dilatability tests of expansive soil and two improved methods,the direct shear tests of expansive soil and two improved methods,and the uniaxial compression tests of expansive soil and soil-cement were carried out respectively.The results show that:(1)The initial moisture content has obvious inhibitory effect on the expansion rate without charge.When the initial water content is 24%,the expansion rate without charge is 7.21%,and when the initial water content is16%,the expansion rate without charge is 16.565%,and the expansion rate without charge is about 2.3 times of the former.The expansion properties of the samples with different moisture content have a uniform regularity: the first stage is the initial stage of the test,the expansion rate almost shows a linear growth,and more than half of the expansion deformation occurs in this stage.The second stage is the deceleration stage,which begins to show exponential slow growth.In the third stage of potential stability,the expansion deformation almost does not change much.There is a negative correlation between the charged expansion rate and the vertical load.The larger the applied load,the lower the charged expansion rate;the smaller the applied load,the higher the charged expansion rate.(2)The overburden load has a strong inhibitory effect on the expansion rate of soil-cement.The corresponding expansion rates of 0,12.5 KPa,25 KPa,37.5KPa and 50 KPa are 12.95%,1.335%,1.255%,1.065% and 1.035%,respectively.When the overburden load is 0,the expansion rate is 12.95%.Compared with the soil-cement with zero load,the soil-cement can greatly reduce the expansion rate under the action of external load.At the same time,cement can also strongly limit the swelling deformation of expansive soil.When the cement content is 1%,3%,5% and 7%,the corresponding no-load expansion rates are 1.305%,0.39%,0.285% and 0.16%,respectively.When the cement content is 0,the expansion rate is 13.35%.(3)By analyzing the stress-strain relationship of uniaxial compression test,it is shown that the cement soil samples with different cement content show the characteristics of strain softening,which can be divided into four stages: the first stage,initial compaction stage;The second stage,the elastic stage;The third stage,plastic strengthening stage;The fourth stage is stress attenuation stage.The elastic modulus under different cement content was obtained by the stress-strain relation curve.(4)Through the direct shear test,it can be seen that increasing the vertical pressure,increasing the cement content and increasing the area replacement rate can obviously improve the shear strength of expansive soil.(5)Through the static equilibrium condition,combined with the elastic modulus obtained from the unconfined compressive strength test,the relationship expressions between cohesion,internal friction angle and area replacement rate are derived respectively,and verified by direct shear test.Figure [48] Table [20] Reference [84]...