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膨润土与砂混合物的膨胀特性是评估核废料深层地质处置工程长期性能的重要指标。对比不同膨润土及其与砂混合物的膨胀试验结果可知,对纯膨润土及其低掺砂率混合物,浸水膨胀完成后蒙脱石孔隙比e_m与竖向应力δ_v在双对数坐标内呈惟一的线性关系,利用该线性关系可预测浸水完成后不同竖向应力下的体积变化量及不同初始状态对应的膨胀力;对高掺砂率混合物,在砂骨架形成之前,e_m-δ_v线性关系成立,随着竖向应力的增大,砂骨架形成,对应的e_m值脱离e_m-δ_v线性关系,混合物中掺砂率越大,脱离该线性关系时的竖向应力就越小。砂骨架形成前,砂颗粒被蒙脱石包围,外力由蒙脱石承担,最终变形量由试样中单位体积蒙脱石的含量决定;砂骨架形成后,竖向应力最终由砂骨架和蒙脱石共同承担。利用砂骨架孔隙比的概念可确定各种不同掺砂率混合物形成砂骨架时的应力起偏点。同时,还可确定混合物能够形成砂骨架的掺砂率范围。
The swelling characteristics of the mixture of bentonite and sand is an important indicator for evaluating the long-term performance of deep geological disposal of nuclear waste. Comparing the swelling test results of different bentonite and its mixture with sand, it can be seen that for the pure bentonite and its mixture with low content of sand, the montmorillonite void ratio e_m and vertical stress δ_v are only linear in double logarithmic scale The relationship between the volume change and the initial expansion force under different vertical stresses can be predicted by using the linear relationship. For the mixture with high content of sand, the linear relationship of e_m-δ_v is established before the formation of sand skeleton With the increase of vertical stress and the formation of sand skeleton, the corresponding e_m values deviate from the linear relationship of e_m-δ_v. The larger the sand content in the mixture, the smaller the vertical stress will be when the linear relationship is removed. Before the formation of the sand skeleton, the sand particles are surrounded by montmorillonite and the external force is assumed by the montmorillonite. The final deformation is determined by the content of montmorillonite per unit volume in the sample. After the formation of the sand skeleton, the vertical stress is finally formed by the sand skeleton Thoroughly shared. The concept of pore-to-void ratio can be used to determine the stress-induced deflection of various sand-mixing ratios to form the sand framework. At the same time, it is also possible to determine the range of sand content that the mixture can form into the sand framework.