渠坡防护对于南水北调膨胀土渠坡变形控制和稳定是非常必要的。通过工程背景和膨胀土特性的分析，认为膨胀土渠坡防护的目标是控制膨胀土的含水量变化，从而抑制膨胀土的裂隙性；指出仅考虑防渗功能的防护方案存在局限性。基于饱和非饱和渗流理论，提出了兼有排水功能的双层结构防护方案；并充分利用非饱和粗、细粒土之间渗透性对比关系随着吸力的变化可以转变的规律，从多种途径实现控制膨胀土边坡含水量变化的目标，从而保证防护方案的长期有效性。

Slope protection is necessary for the deformation control and stability of the expansive soil slopes by the main canal of the Middle Route of South-to-North Water Transfer Project. After analyzing the project background and the properties of expansive soil, the target of slope protection is suggested to be set to control the water content change and to restrain the crack for expansive soil. The defects of the slope protection scheme only with waterproof function are pointed out. On the basis of the theory of saturated-unsaturated water flow, a protection scheme of double layers with water drainage function is proposed. Taking advantage of the law that the comparative relationship of permeability between unsaturated coarse and fine soil would switch over, this kind of scheme would achieve the aim to omnidirectionally control the water content change for expansive soil slope. The more important is that this kind of scheme would be efficient for long time.