黏土抗剪强度演化与酸雨引发滑坡的关系--以三峡库区滑坡为例

RELATION BETWEEN EVOLUTION OF CLAY SHEAR STRENGTH AND LANDSLIDE INDUCED BY ACID RAIN—TAKING LANDSLIDES IN THREE GORGES RESERVOIR AREA FOR EXAMPLE

研究由酸雨诱发的土体抗剪强度变化对滑坡形成可能产生的影响。样品取自三峡库区滑坡新出露的滑面及其邻近面。测试结果显示,滑面上蒙脱石含量明显高于邻近面,相反,邻近面上伊利石含量明显高于滑面。在实验室内用弱酸溶液浸泡蒙脱石、伊利石、高岭石3种重塑土试件,测试不同浸泡时间后试件矿物成分和抗剪强度的变化,以此模拟现场酸雨作用下滑面的形成过程。试验揭示,经酸液浸泡后试件内摩擦角的变化最明显,降低幅度超过1/3,同时黏土矿物成分从含部分伊利石和伊/蒙混层矿物演化成以蒙脱石为主。然后,内摩擦角回升,并消耗蒙脱石生成新的高岭石,此阶段黏聚力的变化微弱。伊利石和高岭石重塑土试件则相对稳定。最后讨论黏土的化学–力学模型。

Possible effects of changes in soil shear strength induced by acid rain on landslide formation are investigated. Soil samples from freshly exposed slip surface and adjacent surface have been studied at two landslides in the Three Gorges Reservoir area, China. A visibly higher smectite content at the slip surface and a dominant content of illite in the adjacent surface are observed. In laboratory, remolded soils are subjected to acid water immersion and tested for changes in their mineral compositions and shear strength after immersion with different durations. The largest change occurs in the internal friction angle, which drops over one-third, going with the change of the original smectitic soil with a substantial illite component into completely smectite dominated soil. Subsequently the internal friction angle rises back, simultaneously with neoformation of kaolinite at the expense of the smectite component. Changes in cohesion are much less significant. The original koalinite-rich and illite-rich samples are found to be much more stable. A chemo-mechanical model of clay is discussed at last.