摘要 在核废料处置库安全使用的设计年限（数万年至数十万年）内，膨润土遇水侵蚀，导致缓冲/回填层致密性降低、渗透性增加，危及核废料处置库安全。膨润土侵蚀是以膨润土凝胶形式迁移，膨润土凝胶的屈服强度就是侵蚀的临界剪切应力。膨润土凝胶颗粒之间的联结靠颗粒间的长程作用，即van der Waals力，颗粒间的联结作用取决于凝胶的结构。本文基于膨润土凝胶结构的分形模型，假设凝胶的屈服强度等于冲刷面上单位面积的van der Waals力的总和，导出了膨润土凝胶的屈服强度（σy）的表达式，表示为凝胶的固体体积率（φs）的幂函数，即σy=σy0φsm，幂函数的指数是凝胶结构分维的函数。膨润土凝胶的屈服强度理论得到了试验数据的验证。
The performance of the bentonite buffer in nuclear waste repository concept relies to a great extent on the buffer surrounding the canister having sufficient dry density. Loss of buffer material caused by erosion remains as the most significant process reducing the density of the buffer. Yield stress of bentonite colloids is a key parameter to express the erosion process of bentonite aqueous solution. A model for the yield stress of aggregates is presented. It incorporates fractal dimension taking into account the solid volume fraction and the aggregate diameter. The model shows that the yield stress(σy) of aggregates increases with the solid volume fraction (φs) as a power law, and is given by σy=σy0φsm, where the exponent(m) is related to fractal dimension(D), and σy0 is a referenced parameter. The relationship between exponent(m) and fractal dimension is validated by published data of aggregates and represents the measured data very well, over a wide range of the solid volume fractions. The referenced parameter(σy0) is calibrated from experiments of yield stress using power law fittings. The agreement between theory and experiments supports the idea that yielding is ultimately caused by the rupture of a few interparticle bonds within aggregates.