以南水北调中线工程、鄂北调水、引江济淮等大型调水工程中的膨胀土问题为研究对象,从膨胀土裂隙性、强度特性和破坏特征等方面,论述了膨胀土边坡稳定的影响因素、边坡破坏机理和强度特性。研究表明,膨胀土的裂隙为胀缩裂隙和非胀缩裂隙两类,非胀缩裂隙是地层中的“原生裂隙”,胀缩裂隙是干湿循环引起的“次生裂隙”。降雨和强度衰减是大多数膨胀土边坡浅层滑动的主要因素,而非胀缩裂隙面的倾向、倾角及强度是控制膨胀土边坡整体稳定的主要因素。膨胀土边坡的失稳,可归纳为“膨胀变形引起的浅层滑动”和“裂隙强度控制的整体滑动”两种破坏模式,膨胀土的边坡稳定分析也应充分考虑膨胀变形和裂隙分布状态的影响;膨胀土的强度指标不能简单地用土体的“综合强度”,而应根据实际地层情况,分别以土块强度和裂隙面强度进行描述。在此基础上,应针对不同的破坏机理进行膨胀土边坡的处治。

Stability factors, failure mechanism and strength characteristics of expansive soil slope are expounded in this paper from aspects of fractures, strength characteristics and failure mode with the middle route project of South-to-North Water Diversion, North Hubei water transfer project, water diversion from Yangtze River to Huaihe River and other large-scale water diversion projects as research background.Fractures in expansive soils can be classified as swelling and shrinking type and non-swelling and shrinking type, of which the latter is protogenesis, and the former belongs to secondary fractures generated by dry-wet cycles.Rainfall and strength reduction are major factors of shallow slide of most expansive soil slopes, while the dip direction, dip angle and strength of non-swelling nor shrinking cracks dominate the overall stability of expansive soil slopes.The instability of expansive soil slope can be summarized as shallow slide induced by expansive deformation and global slide controlled by fracture strength.Therefore, the expansive deformation and fracture distribution should be taken into account in stability analysis, and the strength parameters of expansive soil cannot be regarded simply as the comprehensive strength, but need to be depicted using soil mass strength parameters and fracture strength parameters according to actual geological conditions.On this basis, expansive slopes should be treated in accordance with its specific failure mechanism.