重金属污染土物理性质强度定量关系试验研究

通过室内试验研究土体孔隙液中重金属离子影响土体物理力学性状的机理,采用不同浓度的重金属Cu2+、Zn2+、Pb2+掺入高岭土、伊利石类黏土和钠基膨润土,研究土体界限含液率、不排水抗剪强度随重金属离子浓度的变化规律。试验结果表明:以高岭石、伊利石为主要黏土矿物的低活性土的液限、塑性指数随离子浓度的增加而增大,钠基膨润土则表现出相反的变化规律;低活性黏土的不排水抗剪强度随离子浓度增加而增大,高活性黏土强度则随之减小;基于已有的无污染土体物理力学性状定量联系,分析重金属污染土的不排水抗剪强度与液性指数的定量关系,发现重金属离子引起的不排水抗剪强度的变化可以归结于重金属离子引起的液塑限变化,表明重金属Cu2+、Zn2+、Pb2+污染过程基本没有产生化学反应,其物理力学定量关系与已有的无污染土经验关系式一致。

Experimental study on quantitative physical-strength relationship of heavy-metal-contaminated soils

This study performed a series of laboratory tests for understanding the role of heavy metal ions in the physical-mechanical behaviour.Different kinds of soils, including kaolinite, illite clays and sodium bentonite, were mixed with different concentrations of heavy metals Cu²⁺, Zn²⁺, Pb²⁺ to measure the changes in the Atterberg limits and the undrained shear strength.The testing results show that: the liquid limit and plasticity index of low active soils increase with the ion concentration, but sodium bentonite shows the opposite trend; the undrained shear strength of low-active soils increases with the ion concentration, but conversely for the high-active soils; based on the existing quantitative correlation between physical and mechanical properties of non-polluted soils, the quantitative relationship between the undrained shear strength and liquidity index of contaminated soils is investigated.It is found that the changes of undrained shear strength caused by adding heavy metal ions can be attributed to the corresponding changes in liquid limit and plastic limit.Such a result indicates that there is almost no chemical reaction caused by heavy metal pollution.The physical-mechanical quantitative relationship of heavy-metal-contaminated soils is consistent with the existing empirical relationship of non-polluted soils.