Study On Pb(Ⅱ)or Zn(Ⅱ) Contaminated Soil

This paper mainly studied shear strength,permeability and electrical resistivity of remolded loess contaminated by Pb²⁺ or Zn²⁺, the tests mainly include direct shear test and permeability test, during direct shear test real-time monitoring changes of electrical resistivity. By testing the changes of shear strength and electrical resistivity in different pollution content, void ratio and ages, combined with the changes in electrical resistivity in the process analyze shear strength of the sample, further more explore the relationship between them. While testing remolded loess’ s permeability under different pollution content, different ages. Using the environmental geotechnical flexible wall permeameter introduced from USA to improve the precision of permeability. After a series of system test, collected and analyzed the data, finally got the following conclusion:（1）In the process of direct shear test, with the displacement increasing, the shear strength of Pb²⁺/Zn²⁺ polluted soil increased all through in different pollution content, void ratio and ages. No significant yield point, shear stress throughout the process of polluted soil was "hardening".（2）With the content of Pb²⁺/Zn²⁺ polluted soil increasing, the electrical resistivity decreased. In the process of direct shear test, the current frequency is 50 Hz and 50 kHz, the electrical resistivity decreased and then increased slightly with increasing the displacement. However, the electrical resistivity of Zn²⁺ polluted soil at 50 Hz in 5000mg/kg was unusual. When different void ratio of Pb²⁺/Zn²⁺ polluted soil at direct shear test initial position（the displacement is 0mm）, the electrical resistivity in different current frequencies decreased with void ratio decreasing. Different ages of Pb²⁺/Zn²⁺ polluted soil, the electrical resistivity of different frequencies with the growth rate of ages while the smaller. Electrical resistivity curve of 50 Hz appeared obviously “wave” phenomenon, electrical resistivity curve of 50 kHz is smoother than 50 Hz, to effectively reflect the changes in electrical resistivity of contaminated soil during shear process, so using current frequency of 50 k Hz can better judge shear fracture displacement of contaminated soil.（3）When shear displacement at 6mm, electrical resistivity and vertical pressure had a good linearity in 50 Hz current frequency. The sensitivity and the original electrical resistivity were used to reflect electrical resistivity properties of contaminated soil. The higher pollution degree, the lower original electrical resistivity and the sensitivity were.（4）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.（5）During infiltration different pollution content and ages of Pb²⁺/Zn²⁺ polluted soil with osmotic pressure increasing, hydraulic permeability decreased rapidly. Permeation pressure has great impact on testing hydraulic permeability, so recommended suitable osmotic pressure in penetration tests, should not too large.（6）In different osmotic pressure, different pollution content of Pb²⁺ polluted soil had different changes. When the osmotic pressure at 40-50 kPa, hydraulic permeability of Pb²⁺ polluted soil decreased with Pb²⁺ pollution content increasing. In one osmotic pressure, with ages of Pb²⁺ polluted soil increasing, hydraulic permeability first decreased then increased, and the age of 56 d hydraulic permeability increased more obvious, so the age of Pb²⁺ polluted soil had great impact on hydraulic permeability.（7）In one osmotic pressure, hydraulic permeability of Zn²⁺ polluted soil decreased with Zn²⁺ pollution content increasing, the minimum value is 10-8. At moderate osmotic pressure, hydraulic permeability of Zn²⁺ polluted soil in different ages increased with ages longer.