混合型缓冲回填材料膨胀力试验研究

与纯膨润土相比,混合型缓冲回填材料(膨润土与石英砂混合物)能够实现防渗阻隔能力、热传导性能、力学强度和可施工性能的最佳组合。选用高庙子钠基膨润土(GMZ001)为缓冲回填材料的主料,添加不同比例的石英砂,对掺砂比分别为0、10%、20%、30%、40%和50%的膨润土-砂混合物压实试样进行室内试验。结果表明,混合物的液限、塑限随掺砂率的增大而线性降低;膨胀力随时间呈指数增长。初始含水率较大时,最大膨胀力随初始含水率的增大略有降低。掺砂率一定时,最大膨胀力随初始干密度指数增长。提出了有效黏土密度的概念,建立了一定初始含水率条件下,任意掺砂率和初始干密度的高庙子膨润土-砂混合物最大膨胀力归一化模型,为混合型缓冲回填材料膨胀力的预测与控制提供了依据。

Experimental study of swelling pressure of compacted bentonite-sand mixture

Compared with pure bentonite, bentonite-sand mixture can be used as buffer material in HLW geological disposal to provide low permeability, high thermal conductivity and good workability. Laboratory tests were conducted on compacted mixture of GMZ001 bentonite and quartz sand in different additions of 0, 10%, 20%, 30%, 40% and 50%. Test results show that the liquid limit and plastic limit of the mixture decrease linearly with the increase of sand addition percentage. The maximum swelling pressure of the mixture is exponential increase with initial dry density; but decreases slender with initial water content while the initial water content is higher. By introduction of the concept of effective clay density, an optimum model has been established to describe the relationship between swelling pressure with sand addition percentage and dry density under a certain water content, so as to provide a useful tool for predicting and controlling the swelling pressure of the GMZ001 bentonite and sand mixture in practice.