分散性粘土判别试验研究

应用碎块、针孔、双比重计、孔隙水可溶盐和交换性钠百分比等五种试验方法,结合物理化学性质和矿物成分分析,对西郊、三坪两水库大坝心墙土样进行了多种方案的分散性试验及长期渗流条件下的渗透变形试验和盐分运移试验。认为三坪土样中钠离子的分散作用小于西郊土样,钙镁离子的抑制分散作用大于西郊土样,并且三坪土样中的蒙脱石含量低于西郊土样,因此三坪土样属于非分散性土,西郊土样属于过渡型土。土样施工用水对土样的分散性鉴定结果影响较小,而冲蚀用水对土样的分散性鉴定结果产生大的影响。在长期的渗流条件下土样中钠离子随水流易迁移,河水中的钙离子含量大,进入土体后能抑制土样的分散性,促使土体向非散性的方向发展。结果表明土样中钠离子和钙镁离子含量多寡和相对含量对粘土分散性具有重要的作用,蒙脱石的存在是粘土分散性的重要因素,河水对粘土分散性能将产生显著影响。

Study on identification of dispersive clay soils

The dispersibility as well as seepage distortion and salt transference under long-term seepage condition of soil samples obtained from the clay core wall in Xijiao and Sanping reservoirs were studied by physical and chemical properties of soil and composition of clay mineral and the tests for identification of dispersive clay soils which included double-hydrometer test,pinhole test,crumb test,tests to defermine salt content of pore water and percentage of exchangeable sodium.It was shownd that the soil samples from Sanping reservoir were non-dispersive clays but the soil samples from Xijiao reservoir were of transitional clay.The effect water of used in constructon on dispersive clay was very little,but the effect of scouring water was obvious.Under long-term seepage condition the soil could be improved and became non-dispersive because the sodium-ion in soil could be moved away and the calcium-ion in river water could enter into the soil.The results indicate that the absolute and relative contents of sodium-ion and calcium-magnesium-ion in soil are important to identify dispersive clay soils,while the content of montmorillonoid is one of key factors and the river water affects the dispersibility of clay greatly.