Study On Engineering Properties And Microstructure Of Alkali-contaminated Guilin Red Clay

This research was supported by the Guangxi Natural Science Foundation of Mechanism Study on Weakening of Mechanical Effect of Polluted Red Clay in Guilin City[2017JJA140032].Selected the red clay in the Yanshan area of Guilin as a contaminated soil sample,using sodiumConsidering the two variables of lye mass fraction(0%,4%,8%,12%and 16%)and curing time(7 days,15 days and 30 days),to analy the physico-mechanical properties and microscopic structural changes of alkali-contaminated Guilin red clay The research results are as follows:(1)The physical property test results show that: The color of the alkali-contaminated red clay did not change greatly.The color of the alkali liquor soaked in the soil sample showed a pale yellow color,and the smell of soil changed to the pungent acid smell;With the increase of lye mass fraction during the same curing time,the mass,water content,density of alkali-contaminated red clay first increase and then decrease,and the specific gravity and liquid-plastic limit and plasticity index gradually increase,and the trend becomes slower.When the mass fraction of lye is 12%,there is a threshold for the change of mass,density and water content;With the increase of curing time during the same lye mass fraction increases with the curing time,and the mass,density,specific gravity,liquid plastic limit and plasticity index of alkali-contaminated red clay increase.The rate and void ratio are reduced..(2)The mechanical properties test results show that : With the increase of lye mass fraction during the same curing time,the cohesion increase,the internal friction angle Increase first and then decrease,there is a threshold when the lye mass fraction is 8%,the compressive modulus first increases,then decreases and then increases.When the lye mass fraction is 4%,there is a maximum value,and when the lye mass fraction is 8%,there is a minimum value;The lye mass fraction was the same,and the compressive modulus and shear strength reached a maximum at a curing time of 15 days,reached a minimum at a curing time of 15 days.(3)The microstructure test results show that: The particle structure of alkalicontaminated red clay is mainly composed of sheet structure,and the fracture degree and fractal dimension are reduced compared with uncontaminated soil.With the increase of lye mass fraction and curing time,the fracture and fractal dimension of soil particles decreased first and then increased.In summary,combined with the experimental data of physical and mechanical properties of alkali-contaminated red clay,the action mechanism of alkali-contaminated Guilin red clay was analyzed from a chemical point.It is found that :The alkaline earth reaction is mainly the reaction of sesquioxide and NaOH;the pollution process of alkali contaminated red clay is divided into four stages: alkaline soil reaction stage,salt dissolution stage,cementation stage and dissolution equilibrium stage;there is no obvious time boundary in the four stages,can be carried out at the same time,resulting in the change of physical and mechanical properties and microstructure of the soil.