铅污染黏土微观结构与变形强度特性

MICROSTRUCTURE AND DEFORMATION PROPERTIES OF POLLUTED CLAY BY Pb^(2+) CHEMICAL SOLUTION

为研究铅污染物对黏土微观结构演化和变形特性规律的影响,通过SEM表面微观形貌试验、低温氮吸附试验,研究铅污染黏土的表面微观形貌与孔隙结构特征,微观结构试验结果表明:未受铅污染的原状土颗粒孔隙较少,颗粒以叠片状排列为主;铅污染黏土孔隙发育明显,主要以10 nm左右的中孔为主;随污染物浓度增大,污染黏土的孔径增大,二次孔增多,土颗粒以点–点排列为主;通过开展无侧限抗压强度试验、直剪试验和固结试验,观察铅污染黏土的强度与变形特性,铅污染物对黏土无侧限抗压强度影响显著,随铅污染物浓度的增大,铅污染黏土无侧限抗压强度明显减小。随铅污染物浓度增大,污染黏土抗剪强度减弱,黏聚力c和内摩察角减小。在铅污染物化学溶液的腐蚀作用下,黏土孔隙比e变大,随铅污染物浓度增大,压缩系数和压缩指数cC增大,压缩模量sE减小。

The microstructure and deformation properties of clay was affected by the migration of Pb^2＋ chemical solution. In order to investigate surface morphology and pore structure of polluted clay by Pb^2＋ pollutant,the scanning electron microscope（SEM） test and low-temperature N2 adsorption test were carried out. The results of microstructure tests show that pore of undisturbed clay is small. The soil particles are mainly lamination arrangement. Pore size of polluted clay is mainly near 10 nm,and secondary pore increases. The arrangement of soil particles transformed lamination to point-point under chemical solution. A series of tests are conducted,unconfined compressive strength test,direct shear test and consolidation test,to research deformation properties of polluted clay. The unconfined compressive strength,shear strength and consolidation properties of undisturbed clay were affected obviously by Pb^2＋ chemical solution. The unconfined compressive strength of polluted clay decreased with increasing of Pb^2＋ pollutant concentration. The shear strength index（c, φ） of polluted clay decreased with an increase of Pb^2＋ pollutant concentration. As Pb^2＋ pollutant concentration increased,void ratio（e） of polluted clay increased,compressibility coefficient（α） and compression index（cC） increased,but compression modulus（sE） decreased.