论文部分内容阅读
在垃圾填埋场和场地污染防治工程中,黏土基防渗墙作为原位屏障,已广泛应用于隔离污染物与控制污染地下水的迁移。由黏土与地层混合形成的防渗墙与CaCl_2溶液相互作用后,其渗透性会发生怎样的变化。针对这一问题,使用福建标准砂模拟砂性地层,以4种黏土作为混合材料,通过混合、浇筑和固结以后,对其渗透系数和水分特征曲线进行了实测。结果表明,在10%黏土添加量下,当4种砂-黏土混合土经0.2 mol/L CaCl_2溶液渗透稳定后,其渗透系数相比渗透液为自来水时都有不同程度的增大,但渗透系数增大的倍数没有超过10。此外,CaCl_2溶液在4种砂-黏土混合土中渗透稳定后试样的孔隙率没有发生较大变化,只是小幅地减小了。试验结果分析认为,钙离子与黏土矿物颗粒表面的单价阳离子发生了置换反应,使扩散双电层厚度减小,结合水含量降低,因而有效孔隙率增加,可能是宏观上造成渗透系数变大的主要原因。
In landfill and site pollution prevention and control projects, clay-based cutoff walls as a barrier in situ, has been widely used to isolate pollutants and control the migration of contaminated groundwater. What happens to the permeability of a cutoff wall formed by the mixing of clay and formation with CaCl 2 solution. In response to this problem, Fujian sand was used to simulate the sand formation, and four kinds of clay were used as the mixed materials. After mixing, pouring and consolidation, the permeability coefficient and water characteristic curve were measured. The results show that when 10% clay is added, the permeation coefficient of 4 sand-clay mixed soil increases to some extent when compared with that of permeate when tap water is infiltrated with 0.2 mol / L CaCl 2 solution. However, The multiples of the coefficient increase no more than 10. In addition, the porosity of the sample did not change much after the osmotic stability of CaCl 2 solution in the four kinds of sand-clay mixed soil, but only slightly decreased. The experimental results show that the substitution of calcium ions with the monovalent cations on the surface of the clay mineral particles leads to the reduction of the thickness of the diffused electric double layer and the decrease of the bound water content, thus increasing the effective porosity and possibly increasing the macroscopic permeability coefficient main reason.