Study On Shear Strength And Permeability Of Remolded Loess Polluted By Heavy Metal

This paper mainly studied shear strength and permeability of remolded loess contaminated by Cu²⁺ or Cr⁶⁺, the tests mainly include direct shear test and permeability test, analyze the date by the method of electrical resistivity. Tested remolded loess’ s shear strength and permeability under different dry densities, different pollution levels, different ages. meanwhile tested the electrical resistivity change in the process of direct shear test, further more explored the relationship between shear strength and electrical resistivity; So did to the sample of penetration. After a series of system test, collected and analyzed the data, finally got the following conclusion:（1）To monitored the electrical resistivity change, choose the frequency 50 Hz which is sensitive to soil structure. considering the resistivity error caused by shear displacement, modified the electrical resistivity, got the fixed function. When the dry density is smaller, the shear strength of unpolluted loess was less than polluted loess, when the dry density is larger, the shear strength of unpolluted was larger than polluted loess.（3）With the shear displacement increasing, the polluted loess’ s shear stress increased smoothly than unpolluted loess. The electrical resistivity of polluted loess was smaller than unpolluted loess. With the direct shear test happening, the electrical resistivity of remolded loess decreased, the rules of polluted loess were obvious than unpolluted loess. With the increase of the vertical pressure, the shear strength of loess was greater,the electrical resistivity is smaller. When the loess contaminated by heavy metal, the internal friction angel and cohesion had certain change rules with the void ratio and content changed. With the content of Cu²⁺/Cr⁶⁺ increasing, the electrical resistivity decreased, the content larger, the change of electrical resistivity more stable. With the shear displacement increasing, the shear stress of remolded loess contaminated by Cu²⁺/Cr⁶⁺ increased.（4）Defined the resistivity angel and original resistivity, the resistivity angel reflected the sensitivity which the electrical resistivity to soil structure change, the more sensitive, the less the resistivity, it could monitor the pollution degree and destruction of loess, the original resistivity is electrical resistivity when there were in the absence of vertical pressure.（6）The structure of undisturbed loess was more stable than remolded loess, the coefficient of permeability change slightly, the coefficient of permeability of remolded changed largely. For different dry density remolded loess, the larger the void ratio, the larger the coefficient of permeability. When the pressure of penetration was large, the more the void ratio, the larger the coefficient of permeability.（8）When the pressure of penetration was more than 100 kPa or the void ratio was more than 0.839, the structure of loess was easy to be destroyed, deformation was taken place. In order to gets reliable test date, avoid using excessive penetration pressure or larger void ratio.（9）With the surrounding pressure increasing, the permeability of remolded loess contaminated by Cu²⁺/Cr⁶⁺ decreased gradually. With the polluted level increasing, the permeability coefficient of remolded loess contaminated by Cu²⁺ floated largely than remolded loess contaminated byCr⁶⁺, the permeability coefficient of loess contaminated by Cu²⁺ were less than loess contaminated by Cr⁶⁺.（10）With the void ratio decreasing, the resistivity of polluted loess decreasing, its resistivity before penetration were less than after penetration. With polluted content increasing, the resistivity of polluted loess decreased, when the content were more than 500mg/kg, the rate of decrease slow down. When the content was less, the resistivity of polluted loess before penetration was larger than the resistivity after penetration, when the content was larger, the resistivity was on the contrary. With the age increasing, the resistivity of polluted loess increased, the resistivity before penetration was less than after penetration, the permeability coefficient of remolded loess contaminated by Cu²⁺ increased, the permeability coefficient of remolded loess contaminated by Cr⁶⁺ decreased.