重金属镉污染对土体力学特性的影响及机理分析

为了研究重金属镉(Cd)对土体力学特性的影响规律及其微观机理,开展了不同Cd含量污染土强度、渗透、剪切特性、压汞和扫描电镜试验研究。力学特性试验结果表明:重金属Cd会劣化土体力学特性;随着Cd含量的增加,土体的抗压强度、剪切强度和黏聚力显著降低;而渗透系数、内摩擦角明显增大。扫描电镜试验结果表明:Cd使土颗粒发生团聚,Cd污染土出现大的团聚体,大颗粒增多,土体表面变得比较粗糙,土颗粒之间的接触形式增多,出现点-面接触和边-面接触;且团聚体间的孔隙较大。压汞试验表明:随着Cd含量的增加,污染土中孔径大于1μm的孔隙体积明显增加。污染土的微观结构和孔隙分布的改变是Cd污染土力学特性变化的本质原因。

Effect Cadmium Content on the Mechanical Properties and Microstructure of the Soil

To provide the mechanical properties and microstructure of cadmium contaminated soil. Unconfined compressive strength test, permeability test, shear test and microstructure tests were conducted to investigate the engineering properties and microstructure of cadmium-contaminated soils with different content. Results showed that cadmium degradate of mechanical properties of soil. The unconfined compressive strength, shear strength and cohension of the cadmium contaminated soil decreased with cadmium content, but the hydraulic conductivity and internal friction angle increased. Microstructure tests showed that a larger aggregation formation, with a larger void space in soils as the cadmium content increased. the laminated sheet structure of soil will be gradually destroyed. The contact between the soil particles changed from surface-to-surface contact to point-to-surface contact or edge-to-surface contact. MIP test results show that the total void volume increased as the cadmium content. The cadmium increased the pore volume of soil pores, which the diameter larger than 1 mm. The change in mechanical properties and microstructure of cadmium contaminated soil can be attributed to the change in the microstructure and pore volume distribution of cadmium contaminated soil.