压实膨润土-砂混合物最佳养护湿度研究  

Optimal curing humidity for compacted bentonite-sand mixtures

作　　者：张虎元[1,2] 丁志南 谭煜 朱江鸿 曹志伟 ZHANG Hu-yuan;DING Zhi-nan;TAN Yu;ZHU Jiang-hong;CAO Zhi-wei(School of Civil Engineering and Mechanics,Lanzhou University,Lanzhou,Gansu 730000,China;Key Laboratory of Mechanics on Disaster and Environment in Western China of Ministry of Education,Lanzhou University,Lanzhou,Gansu 730000,China)

机构地区：[1]兰州大学土木工程与力学学院,甘肃兰州730000 [2]兰州大学西部灾害与环境力学教育部重点实验室,甘肃兰州730000

出　　处：《岩土力学》2021年第11期2925-2933,共9页Rock and Soil Mechanics

基　　金：国家自然科学基金项目(No.41972265)。

摘　　要：高放废物缓冲材料压实成砌块之后需要进行养护保存,防止砌块发生干缩开裂等劣化现象。以压实膨润土-砂混合物室内小试样为研究对象,模拟砌块在不同初始含水率(11.23%~21.63%)和环境相对湿度(33%、75%、85%和100%)条件下的劣化情况,寻求最佳养护湿度。试样养护过程中,用天平称量质量变化,用游标卡尺测量尺寸变化,养护平衡后测试导热性能。试验结果表明:试样养护过程中的水分演化规律符合土-水特征曲线。养护湿度为33%、75%和85%时,试样均干燥失水,体积收缩,产生干缩裂隙;养护湿度为100%时,较低初始含水率(11.23%~14.99%)试样发生吸湿膨胀,较高初始含水率(17.22%~21.63%)试样发生失水收缩,但是试样表面均没有观察到明显裂隙产生。初始含水率为17.22%的试样在100%相对湿度养护条件下,含水率以及体积变化为最小,为最优的砌块养护条件。并且,处置库所使用的工业尺度砌块的最优养护条件可以通过小试样的土-水特征曲线进行预测,其裂隙发育情况可以通过导热系数进行定量评价。The buffer blocks used in deep geological repositories of high-level radioactive wastes(HLW) should be cured in an appropriate environment to prevent the deterioration of buffer blocks such as desiccation shrinkage and cracking. In this study, the bentonite-sand mixtures with different initial moisture contents(11.23%-21.63%) were compressed in the laboratory to simulate the production of buffer blocks. The bentonite-sand mixtures were cured at different relative humidity(RH) of 33%, 75%, 85% and 100% in order to find the optimum curing humidity. During the curing process, the periodical mass change was weighed by a balance,the size change was measured by a vernier caliper, and the thermal conductivity was tested after the curing was balanced. The test results indicate that the moisture variation of bentonite-sand mixtures during curing was consistent with the soil-water characteristic curves(SWCCs) of the mixtures. When the compacted bentonite-sand mixtures were cured at the relative humidity of 33%, 75% and 85%, the samples were dehydrated and became dried, resulting in desiccation shrinkage and cracking. When the relative humidity was100%, the mixtures with a lower initial moisture content of 11.23%-14.99% tended to absorb moisture from the environment and swelled. While the mixtures with a higher moisture content of 17.22%-21.63% were desiccated to shrink, but no obvious cracks were observed on the surface of these cured specimens. Under the curing condition of RH = 100%, the variation of water content and volume of the sample with an initial water content of 17.22% was the minimum, which was considered as the optimum curing humidity for buffer blocks. The optimal curing conditions(optimum RH) of industrial-scale buffer blocks used in the disposal repository can be estimated by the SWCCs of the small buffer blocks, and the development of drying shrinkage crack can be quantitatively evaluated by the thermal conductivity of buffer blocks.

关 键 词：高放废物 膨润土-砂混合物 缓冲砌块 养护 相对湿度 

分 类 号：TU443[建筑科学—岩土工程]