| The industrialization process of our country has brought great pollution to the environment.Although the government has strengthened the environmental treatment,the low concentration waste liquid will weaken the strength of rock and soil.Because of the variety of soil,complex structure and numerous pollution sources,there are still many problems in the research of polluted soil.This paper mainly studies the change rules of physical and mechanical properties and microstructure characteristics of Guilin Red Clay before and after being polluted by alkali solution with different pH values.A series of indoor tests are carried out.The main contents of the study are as follows:1.The basic characteristics of Guilin red clay were briefly described.Na OH was selected as the alkali pollutant.According to the pH value standard of industrial wastewater discharge,the pH of the test solution was 7,9,10,11 and the initial water content was controlled as 21%;2.Alkali solution reacts in red clay,and produces substances with high quality Fe（OH）3、Al（OH）3 etc.The soil sample mass,density,proportion and pore ratio increase with the increase of pH value;when pH is 11,its mass growth rate is the largest;the increase is 59.1%;the liquid plastic limit and plasticity index of alkali polluted red clay decrease,and the trend decreases gradually;3.The water evaporation rate of fracture sample is fast in the early stage.Although a large number of alkali solution erodes the interior of red clay,the pores are still filled with sediment,and the smaller fractures are recombined.With the increase of pH value of Na OH solution,alkali solution erosion degree is intensified,and the fracture development is slow,and no crack appears when pH is 10 and 11;4.With the increase of pH value,the linear shrinkage of red clay becomes larger and larger after alkali pollution,and its shrinkage deformation is bigger and bigger;the compression coefficient and modulus of the samples are changed by the pH value of alkali solution,and the compressibility of polluted red clay is larger;the triaxial test results show that the damage characteristics and evolution law of red clay are basically the same,and with the increase of pH value of alkali solution,the damage variable is in the form of damage variable The stress-strain relationship of alkali polluted soil is still strain hardening type,and the failure forms of soil are waist drum failure,and the change of confining pressure and the increase of pH value have an effect on the damage of red clay;5.There is a certain relationship between the macro properties and microstructure of the alkali polluted red clay.The strength of red clay is mainly related to the attraction between particles,the water film connection between particles and the cement between particles.The structure of red clay after alkali solution immersion is destroyed,and the connection between particles breaks and forms"gully".With the increase of pH value,Al and Fe elements are dissolved,and the large particle unit is gradually replaced by small particle units,and the structure of soil is internal It becomes more uneven and uneven,and the pore develops,which greatly weakens the structural strength of red clay.Therefore,the mechanical strength of alkali polluted soil generally shows a trend of attenuation. |
