利用膨润土的膨胀和稠度特性对GCL渗透系数进行预测的试验研究

以土工合成粘土衬垫(Geosynthetic Clay Liner,GCL)在尾矿库防渗层中的应用为背景,研究不同浓度重金属离子(Cu和Zn)作用下,膨润土的自由膨胀量、液限及GCL渗透系数的变化规律,并分析它们之间的对应关系。试验结果显示,当重金属离子浓度在0.01mol/L到0.1mol/L之间递增时,膨润土的自由膨胀量和液限会随着重金属离子浓度的增大而大幅度减小,但当重金属离子浓度从0.1mol/L增加到0.5mol/L时,膨润土的自由膨胀量和液限则只有微小变化。在渗透试验中,当渗透溶液中重金属离子浓度小于0.01mol/L时,GCL的渗透系数能够保持稳定;但当重金属离子浓度大于0.02mol/L后,GCL的渗透系数会随着渗透溶液中重金属离子的浓度增加而不断升高。研究结果表明,当尾矿库渗滤液中重金属离子浓度大于0.02mol/L时,GCL的渗透系数与膨润土的自由膨胀量和液限之间具有良好的数学对应关系,可以利用自由膨胀量和液限对渗透系数进行预测。

Relationship between hydraulic conductivity and swell index and liquid limits of GCL

Geosynthetic clay liner (GCL)has been increasingly used as a hydraulic barrier for tailing impoundment.Under the action of different concentrations of heavy metal ions (heavy metal compounds are CuCl2 and ZnCl2 ),the change regulation of the free swell index, liquid limits and GCL hydraulic conductivity is researched,and the correspondences between them are analyzed.It is shown that when the concentration of heavy metal ions ranges from 0.01 mol/L to 0.1 mol/L,the free swell index and liquid limits decease with the increase of concentrations of heavy metal ions.However,further increasing of the heavy metals ions concentration (from 0.01 mol/L to 0.5 mol/L)can’t cause the two index properties decrease continually.In the permeation test,when the concentration of heavy metal ions ranges is lower than 0.01 mol/ L, the hydraulic conductivity of GCL can remain stable. By contrast, when the concentration of heavy metal ions is up to 0.02 mol/L,the hydraulic conductivity of GCL increases with the increase of heavy metals ions concentration.Results of the study show that the index properties of a bentonite has good correspondence with the hydraulic conductivity of the corresponding GCL when the heavy metal ions concentration is higher than 0.02 mol/L and they can be used to estimate the hydraulic conductivity.