Experimental Study On The Dynamic Characteristics Of Heavy Metal Contaminated Expansive Soil Under Cyclic Loading

Heavy metal contaminated expansive soils are a special kind of contaminated soils with more complex properties.The basic physical and mechanical properties of contaminated expansive soils and the dynamic characteristics of soil deformation,pore pressure and modulus of elasticity under cyclic loading were studied through laboratory tests on Nanyang expansive soils mixed with different concentrations of heavy metals(Pb²⁺,Zn²⁺).The test results are summarized and the dynamic characteristics of heavy metal contaminated expansive soils are analyzed in order to better guide the treatment of contaminated soils,which has certain engineering value and theoretical significance.The main conclusions are as follows:The physical and mechanical properties of expansive soils polluted by heavy metals(Pb²⁺,Zn²⁺)are compared and analyzed.With the increase of heavy metal ions(Pb²⁺,Zn²⁺)concentration in soils,the maximum dry density,permeability and CBR expansion rate of polluted expansive soils increase,but the optimal moisture content,unconfined compressive strength,CBR value and peak stress and strain strength decrease.The dynamic characteristics of heavy metal(Pb²⁺,Zn²⁺)contaminated expansive soils under cyclic loading were studied,including deformation,dynamic pore pressure and dynamic elastic modulus.The effects of different concentrations of heavy metal ions,vibration times,dynamic stress amplitude,vibration frequency and confining pressure on the axial cumulative deformation,critical dynamic stress,dynamic pore pressure and dynamic elastic modulus of contaminated expansive soils are considered.The results show that the cumulative axial deformation increases with the increase of heavy metal ion concentration and dynamic stress amplitude in contaminated expansive soils,while the cumulative axial deformation decreases with the increase of vibration frequency and confining pressure,and the critical dynamic stress decreases with the increase of heavy metal ion concentration in contaminated expansive soils and increases with confining pressure.Dynamic pore pressure increases with the increase of heavy metal ion concentration,dynamic stress amplitude and confining pressure of contaminated expansive soils,but decreases with the increase of vibration frequency.The dynamic elastic modulus decreases with the increase of heavy metal ion concentration,vibration frequency and dynamic stress amplitude,while the dynamic elastic modulus increases with the increase of vibration frequency and confining pressure,and the curve of dynamic elastic modulus with dynamic strain is hyperbolic.