Ca^(2+)浓度对膨润土掺砂混合土渗透性能的影响

Influence of Ca^(2+) concentration on hydraulic properties of bentonite-sand mixtures

垃圾填埋场底部铺设含黏土或膨润土掺砂混合土的防渗系统,防止渗滤液流入地下污染周边环境。采用模型试验研究Ca^(2+)离子浓度和基础局部沉降对膨润土掺砂混合土渗透特性的影响。试验结果表明Ca^(2+)浓度对膨润土掺砂混合土的渗透性能有较大影响,渗透液中Ca^(2+)浓度超过一定值后混合土渗漏;Ca^(2+)离子浓度与发生渗透时间之间有很大关系,浓度越高发生渗透的时间越短;同样沉降量条件下,含Ca^(2+)离子溶液渗透的混合土均发生渗漏,而用蒸馏水作渗透液的没有出现渗漏;钠基膨润土遇Ca^(2+)离子溶液后,当Ca^(2+)离子浓度大于两倍Na+就会发生离子交换,钠基膨润土转化为钙基膨润土,混合土的防渗性能下降。因此开展Ca^(2+)离子浓度对膨润土掺砂混合土渗透特性的研究具有较好的理论和实际意义。

A liner system containing clay or bentonite-sand mixtures is installed on the bottom of a landfill to prevent contaminants from flowing into the surrounding ground. The influence of Ca^2＋ concentration and local settlement on hydraulic properties of bentonite-sand mixtures is studied by model tests. It is shown that Ca^2＋ concentration has significant influence on the hydraulic properties, while the bentonite-sand mixtures leak with Ca^2＋ concentration more than 3.00g/L. Ca^2＋ concentration correlates with seepage time, which is shortened with the increase of Ca^2＋ concentration. Under the same settlement conditions, leakage occurs to the bentonite-sand mixtures infiltrated by Ca^2＋ ion solution but not to those by distilled water solution. When Ca^2＋ concentration is higher than two times Na＋ in solution, the sodium bentonite converts to calcium bentonite, and the hydraulic properties of the bentonite-sand mixtures decrease. Therefore, it is of theoretical and practical values to investigate the influence of Ca^2＋ concentration and local settlement on hydraulic properties of the bentonite-sand mixtures.