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为了客观评估高放核废物地质处置库开挖建设和封存初期围岩面临的非饱和岩土力学问题,针对一种高放核废料储存介质(硬黏土)开展不同干湿循环试验,研究该材料的土水特性变化规律。基于湿度控制吸力方法,研制黏土非饱和测量系统,利用该系统对硬黏土进行不同干湿循环试验,对比分析干湿循环次数和基质吸力变化梯度对硬黏土的土水特征曲线的影响。研究结果发现:干湿循环次数对这种硬黏土的土水特征曲线影响较大,基质吸力变化梯度影响则很小。同时,结合不同干湿循环条件下硬黏土核磁共振细观测试结果,分析出干湿循环和基质吸力对硬黏土的土水特性影响机制。通过分析不同干湿条件下硬黏土的含水分布特征,定量出该硬黏土干湿过程不同孔径内含水变化,揭示其不同孔径含水量等比例变化与水的吸附状态密切相关,为深入理解硬黏土干湿循环过程土水特征曲线变化规律提供试验依据,为高放核废物地质处置围岩水力特性评估奠定试验基础。
In order to objectively evaluate the unsaturated rock mechanics problems faced by the surrounding rock during the excavation and storage of the high-level nuclear waste geological repository and different wetting-drying cycles for a high-level nuclear waste storage medium (hard clay) Soil water characteristics of the law of change. Based on the humidity control suction method, a clay unsaturated measurement system was developed. The system was used to carry out different wetting and drying cycles tests on hard clay. The influences of the number of wetting and drying cycles and the gradient of substrate suction on the soil-water characteristic curve of hard clay were analyzed. The results showed that the number of wetting and drying cycles had a great influence on the soil-water characteristic curve of this kind of hard clay, and the influence of gradient of matrix suction was small. In the meantime, the influence mechanism of wetting and drying cycles and matrix suction on the soil-water characteristics of hard clay was analyzed based on the results of the microscopic tests of hard clay under different wet-dry conditions. By analyzing the water distribution characteristics of hard and humid under different dry and wet conditions, the change of water content in different pore sizes of dry and wet hard clay was quantitatively determined. It is revealed that the ratio of water content and pore water content is closely related to the adsorption state of water. This paper provides experimental basis for the variation rule of soil-water characteristic curves during the process of clay wet-dry circulation, which lays a foundation for the evaluation of hydraulic characteristics of surrounding rocks treated by high-level radioactive waste.