盐溶液侵蚀下砂-膨润土混合土化学固结行为研究

Study on chemical consolidation behavior of sand-bentonite mixed soil under saline solution erosion

环境溶液中含盐量的增加可造成细粒土含量较高的土体不可忽略的沉降变形。本文采用砂-膨润土混合土作为试验材料,CaCl2作为试验溶液,发现随着孔隙液浓度从0 mM增加至1000 mM,土样渗透系数上升逾10倍,体积压缩系数下降65%~71%。通过高浓度溶液渗透对土样进行化学固结,由此造成的土样体积应变最高达20%。提出了化学体积压缩系数的概念,并将其引入考虑了化学-力学耦合作用的固结方程中,根据模拟结果对高盐溶液侵蚀下砂-膨润土的固结行为进行了机理分析:当污染物向土样内部迁移,土样出现体积收缩趋势,超静孔压逐渐增大,而后超静孔压随着排水固结消散,土样发生压缩变形。

For the soil body with high soil fines content,the increase of salt content in environment solution will cause the settlement deformation which cannot be ignored.In this paper,sand-bentonite mixed soil was used as the experimental material,and CaCl2 solutions were prepared for laboratory tests.It was found that with the increase of pore fluid ionic concentration from 0 mM to 1000 mM,the hydraulic conductivity of soil increased more than 10 times and the volumetric compressibility coefficient decreased by a percentage of 65 to 71.The soil samples were chemically consolidated through osmosis of high concentration solution,and it was found that the resulting maximum volume strain of soil reached 20%.The concept of chemical volumetric compressibility coefficient was proposed and introduced into the consolidation equation which considered the chemo-mechanical coupled effect.According to the simulation results,the mechanism of sand-bentonite consolidation behavior under high salt solution erosion was analyzed.It was found that with the migration of pollutants into the soil sample,the excess pore pressure increases gradually due to the volume shrinkage trend of the soil sample.Then,the excess pore pressure dissipates with the drainage consolidation,resulting in compression deformation of the soil sample.