Experimental And Model Study Of Triaxial Shear Strength Of Soil Eroded By Heavy Metal Cu²⁺

With the acceleration of urbanization and industrialization, the construction encountered an increasing number of heavy metal pollution site, seriously affecting the engineering quality and safety. A series of engineering problems has been paid great attention. The study of eroded soil intensity variation mechanism and intensity model is one of the key issues of contaminated sites, meanwhile, is the important issue in the field of environmental geotechnical engineering. As a research object of the remolded samples which mixing the CuCl2 solution with different types of soil, to carry out the indoor shear strength experiment using the temperature controlled triaxial apparatus. To study the impact of heavy metal concentration on the remolded samples strength. A double stress variable strength model is established when introduced osmotic suction, which is suitable for the eroded soil.The main research work and achievements are as follows:(1) Demonstration of osmotic suction as independent stress state variables. Saturated erode soil which is a three-phase porous medium compares soil particles, the double layer diffusion and pore fluid.Volume fraction is introduced to characterize the internal structural changes in the soil. Taking into account the contribution of osmotic suction to analysis the force-balance of representative soil element volume, three independent stress state variables geting controlled soil structural balance are gained, ?-uf ??? R-A.(2) Consolidated undrained triaxial shear test of remodeling kaolin soil mixed with CuCl2 solution. The results showed that erosion of different concentrations of Cu2+ has a greater effect on the strength properties of the soil. With Cu2+ concentration increases, the axial stress of soil samples decreases, the effective cohesion and angle of internal friction are reduced, weakening the soil shear strength. Osmotic suction is Introduced as a variable parameter in analysis of force balance of soil unit. Extend Moore Coulomb strength model is established combing the normal stress and osmotic suction through the test results by fitting space plane.(3) Consolidated undrained triaxial shear test of remodeling Guizhou clay and Beijing silty clay mixed with CuCl2 solution. The extended Mohr-Coulomb model is establishied based on normal stress and the shear strength model of erode soil is promoted. The results show that with the Cu2+ concentration increases, the axial stress of soil samples decreases, the effective cohesion and angle of internal friction are both reduced.The change of strength characteristic of the sample is similar to the kaolin sample results obtained. There is a certification for the strength model of erode soil established before through the test results by fitting space plane.(4) Analysis the mechanism of action between Cu2+ and clay particles. As we all know,there is a essential characteristic of clay particle with negatively charged surface. The mechanisms of the effect of Cu2+ on the macroscopic soil strength contain ion exchange, electrostatic forces and the change of electric double layer thickness.