中文摘要：

西北地区灌溉引发大量黄土-红层泥岩滑坡,其中快速滑坡的活动机理与灌溉溶滤后泥岩中易溶盐含量降低及其不排水抗剪强度密切相关。本文以兰州及其附近两处白垩系红层风化泥岩为例,探讨了溶滤后风化泥岩不排水抗剪强度的变化特征。结果显示,溶滤后风化泥岩不排水强度显著降低。其内在机理涉及两方面的水-土综合作用,其一,易溶盐流失,风化泥岩颗粒间胶结弱化,粗颗粒分散,粘粒增多;再之,粘粒增多后,泥岩内产生较高的孔隙水压力,有效应力随之降低。

英文摘要：

Aiming at better understanding the variation in undrained shear strength of clayey soil after salt leaching and its mechanism,two types of weathered red mudstone near and from Lanzhou City were sampled, and their triaxial consolidated undrained shear strength was investigated after being leached various times. Results showed that the weathered red mudstone＇s undrained shear strength was remarkably reduced after leaching,mainly through water-soil physic-chemical interactions in two ways. One is that the effective friction angle and cohesion of the sample would reduce to loss of bonding salts. The other is that higher pore water pressure could be built up during shearing due to increment of clay fraction led by disaggregation of coarse particles,leading to decrease in effective normal stress and then in shear strength.