Experimental Study On Physical And Mechanical Properties Of Red Clay Contaminated By Alkali

With the vigorous development of the our country economy,the environment problem more and more attention to the survival of humans,the environment by pollution is becoming more and more serious.For air quality,the ground surface water,groundwater and ecological environment pollution early research and conservation has been carried out,but for the soil pollution problem awareness is not high.This subject is a new research direction.This paper is based on the key project of science and technology in Guangxi--Geotechnical engineering characteristics of red clay in Guilin karst area pollution research [KY2015ZD055] to carry out a series of studies.Select the Guilin Yanshan red clay,sodium hydroxide(NaOH)as the base class of pollutants,around this topic,sodium hydroxide solution with different concentration on the impact of physical and mechanical properties of red clay,elucidate the interaction between alkali and red clay.Specifically as follows:Physical property tests include water content test,specific gravity test,limit moisture content test and appearance test.Physical properties tests showed: The red clay was soaked in sodium hydroxide solution for 7 days,and the color of the solution changed from transparent colorless to brown and no obvious change of soil samples,accompanied by acid odor;The proportion of red clay was slightly larger than that of alkaline soil,and the proportion increased with the increase of alkali concentration;With the increase of the concentration of alkali solution,the liquid,plastic limit and plasticity index showed a gradually increasing trendMechanical properties test including direct shear test and compression test.The experimental results show that the mechanical properties: The shear strength of red clay samples is smaller after pollution,with the increase of alkali solution concentration,the shear strength decreases gradually,the shear strength index of cohesion and internal friction angle decreased,The compression modulus decreases and the compression coefficient increases.Based on the above experimental results,the reaction mechanism of alkali and red clay was studied.The interaction between sodium hydroxide and red clay particles caused the change of physical and mechanical properties of red clay.The alkali soil interaction can be found in four stages by the reaction of alkali to red clay: Hydrolysis stage,erosion stage,cementation stage and dissolution stage.The above four stages are explained by the chemical reaction mechanism.The four stage of alkali soil interaction is caused by the change of the physical and mechanical properties of red clay.The red clay is chemically reacted with alkali,and the free oxide is coated on the surface of clay mineral or filled in the gap of clay mineral aggregate,the original structure of red clay is destroyed and the cementation force between particles is weakened,with the erosion of the process,the formation of a number of floc,crystal and colloid to increase the cementation,the soil is relatively dense and the shear strength is improved,In the late stage of curing,the formation of the soil was gradually dissolved,the soil structure became loose,the cementation force between the soil particles was weakened,and the shear strength of the red clay was reduced and the compressibility increased.There are no strict time limits for the four stages of alkali soil interaction...