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设计了专门的浸水试验装置,测定了膨润土-石英砂混合物在非膨胀条件下吸水引起的水分分布及膨胀应力变化,研究了混合型缓冲回填材料非饱和水力学性质。试验结果表明,干密度约1.70 g/cmP3、掺砂率为30%的GMZ001膨润土-砂混合物的水分扩散系数与含水率的关系呈U型变化,即随着含水率增加,汽态水分扩散系数减小,液态水分扩散系数增大。根据理论推导建立非饱和导水率估算方程。计算发现,混合物的非饱和导水率随含水率的增大而增大。其中,汽态水分非饱和导水率先增大后略有减小,液态水非饱和导水率始终增大。试验发现,试样吸水后干密度趋于均匀化,试样内部不同位置的应力发展与水分迁移过程密切相关:渗入端的应力在入渗初期增长很快,随后减慢;渗出端的应力持续稳定增长;入渗96 h后,两端应力趋于一致。估算出的水分扩散系数及非饱和导水率,可用于评价混合型缓冲回填材料阻隔核素迁移安全性。
A special immersion test device was designed to measure the water distribution and swelling stress changes caused by water absorption of bentonite-quartz sand mixture under non-swelling conditions. The unsaturated hydraulic properties of the hybrid buffer backfill material were studied. The results showed that the relationship between water diffusion coefficient and moisture content of GMZ001 bentonite-sand mixture with a dry density of 1.70 g / cmP3 and a sand content of 30% was U-shaped. That is to say, with the increase of water content, the moisture diffusivity Decrease, liquid water diffusion coefficient increases. Based on the theory, the estimation formula of unsaturated hydraulic conductivity is established. The calculated results show that the unsaturated hydraulic conductivity of the mixture increases with the increase of water content. Among them, the unsaturated hydraulic conductivity of water vapor increases first and then decreases slightly, and the unsaturated hydraulic conductivity of liquid water increases all the time. It is found that the dry density of the sample tends to be homogenized after water absorption. The stress development at different positions inside the sample is closely related to the process of water migration. The stress at the infiltration end increases rapidly at the initial stage of infiltration and then slows down. Growth; infiltration 96 h, the stress at both ends tend to be the same. The estimated moisture diffusivity and unsaturated hydraulic conductivity can be used to evaluate the migration nuclide transfer safety of mixed buffer backfill materials.