Study On The Properties Of Wind-sand Modified Expansive Soil And The Stability Of Subgrade Slope

Expansive soil is a kind of cohesive soil that is common in engineering construction.It has obvious characteristics of water absorption expansion and water loss shrinkage.When modern engineering construction is carried out in an area covered by expansive soil,the expansion often occurs due to the expansion or contraction of the expansion soil foundation.Serious damage.The method commonly used in engineering to solve the problem of expansive soil damage is to improve the expansive soil so that its strength meets the requirements of engineering construction.According to the existing research results and engineering examples,the improvement method is mainly to add lime,fly ash,HEC curing agent,HTAB and STW type soil stabilizer to the expansive soil.These modifiers can effectively increase the expansive soil Stability and strength,but there will be shortcomings such as serious pollution and excessive cost.Therefore,this paper proposes to use weathered sand as an modifier to improve the expansive soil.Direct shear test,unconfined compression test and bearing ratio test were carried out on the improved expansive soil to study the changes with the amount of weathered sand.The change law of expansive soil’s shear strength,unconfined compressive strength and CBR value.The research results show that with the increase of the amount of weathered sand,the shear strength and unconfined compressive strength of the improved expansive soil both increase first and then decrease.When the amount of sand added is 20%,the strength reaches Maximum value;as the amount of sub-weathered sand increases,the CBR value of the improved expansive soil gradually increases.The research results provide a scientific basis for the use of weathered sand to improve the physical properties,swelling and shrinking properties,and strength properties of the expansive soil,and provide a new technology with high efficiency,environmental protection,turning waste into treasure,and strong operability for the treatment of expansive soil in the future.The main research contents of this article are as follows:(1)The distribution characteristics of expansive soils in China,as well as the special geological characteristics and fissure characteristics of expansive soils are introduced.Internal and external factors.(2)The free swelling rate,liquid-plastic limit,optimal water content,specific gravity,etc.of the original expansive soil were tested indoors.The free swelling rate of the original expansive soil was measured to be 53.5%,and the liquid-plastic limit was 52.9%And 25.3%,the optimal water content is 19.8%,and the specific gravity is 2.729.According to the liquid-plastic limit and the free expansion ratio,the expansive soil is judged as a high-liquid-limit weak expansive soil.(3)Laboratory tests on mechanical properties such as direct shear test,unconfined compression test,and CBR test were carried out on weathered sand-modified expansive soil.It is concluded that as the amount of sand added increases,the internal friction angle and CBR value of the improved expansive soil gradually increase;it is concluded that the amount of expansion of the improved expansive soil decreases gradually as the amount of sand added increases;It is concluded that the shear strength,compressive strength,and cohesive strength of the improved expansive soil increase first and then decrease with the increase of the sand content,and all reach the conclusion when the sand content is 20%.(4)With the Jilai Intercity Railway as the background,the effect of weathering sand on improving expansive soil was verified according to the actual project.The results verified that the slope settlement after meeting the appropriate amount of weathering sand meets the design requirements.Numerical simulation by ABAQUS shows that when the sediment content of expansive soil is 20%,the deformation and displacement of slope are the minimum,and the stress is also the minimum.