钠质膨润土渗透性与膨胀性及可塑性的相关性

Correlation between permeability, swelling, and plasticity of sodium bentonite

盐溶液与钠质膨润土的化学相容性研究对评估防污屏障的服役性能起到重要作用,为此,采用渗透试验、自由膨胀试验和界限含水率试验研究不同浓度的NaCl溶液和CaCl 2溶液对钠质膨润土渗透性、膨胀特性、可塑性的影响规律.结果表明,随着溶液中阳离子浓度增加,钠质膨润土的渗透系数增大,膨胀指数先增长再下降,塑性指数减小;相同浓度下,钠质膨润土在NaCl溶液中的渗透系数低于在CaCl 2溶液中的渗透系数,膨胀指数高于CaCl 2溶液中的膨胀指数,塑性指数高于CaCl 2溶液中的塑性指数;12~800 kPa的固结压力范围内,在CaCl 2溶液中,渗透系数分别与膨胀指数、塑性指数具有较好的相关性;在NaCl溶液中,当溶液浓度超过临界浓度(200 mmol/L)时,渗透系数与膨胀指数、塑性指数也具有较好的相关性.因此,界限含水率测试和自由膨胀试验可作为工程中初选渗透系数的手段.

The chemical compatibility study between salt solution and sodium bentonite plays an important role in evaluating the service performance of the antifouling barrier.Effects of different concentrations of NaCl solution and CaCl 2 solution on the permeability,swelling characteristics,and plasticity of sodium bentonite were studied by hydraulic conductivity test,free swell test,and water ratio limit test.Experimental results show that as the concentration of the cations in the solution increased,the hydraulic conductivity of the sodium bentonite increased,the swell index first increased and then decreased,and the plasticity index decreased.At the same concentration,the hydraulic conductivity of the sodium bentonite in NaCl solution was lower than that in CaCl 2 solution,and the swell index and plasticity index were both higher than those in CaCl 2 solution.Within the consolidation pressure range of 12-800 kPa,the hydraulic conductivity had a strong correlation with the swell index and plasticity index in CaCl 2 solution;in NaCl solution,when the solution concentration exceeded the critical concentration(200 mmol/L),the hydraulic conductivity also had a strong correlation with the swell index and plasticity index.Therefore,it is feasible to replace the hydraulic conductivity test with water ratio limit test and free swell test.