There existed 387 km long expansive soil along the Middle Route Project of South-to-North Water Diversion, and more than 100 landslides of certain scale occurred during the construction period. Through detail analysis of massive landslides, deformation monitoring and in-situ test of water physical-chemical index of the soil body, two main types of slope failures are revealed, namely the shallow expansive-contraction creep and the deep structural interface-controlled sliding. The surface lay-er substitution by cement-improved expansive soil was applied to prevent the reformation action from atmospheric environment;the surface water cutoff combined with underground drainage measures could mitigate the adverse influence of water on soil body and the structural interface. Aiming to the slope structure with long and large low-angle interfaces or soft interlayer, the anti-sliding structural measures should be used to avoid the sliding along the structure plane and maintain the long-term stability of the channel.%南水北调中线工程干线有387 km为膨胀土或膨胀岩渠段，施工期间累计发生有一定规模的滑坡超过100处。通过对工程施工期滑坡的大量解剖、变形位移监测、土体水理指标原位观测，揭示膨胀土渠坡变形破坏主要有浅表胀缩型和较深层结构面控制型滑坡破坏两类。采用水泥改性土换填覆盖处理可以有效减少渠坡膨胀土受大气环境改造的作用，采用地面截渗和地下引排措施可以减少水对土体及结构面的不利影响。当坡体存在长大缓倾角结构面或层间软弱带时，为防止沿结构面产生滑动并维持渠坡长期稳定，必须采取结构抗滑措施。
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