干湿循环对硬黏土的土水特性影响规律研究

 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。

Experimental study on the water retention properties of the hard clay under cyclic suction conditions

In order to understand the unsaturated host medium of the high-level radioactive nuclear waste disposal repository in deep geological formation，a series of hydration and dehydration tests were performed on the hard clay which has been considered as the potential host medium for storage of the high-level nuclear waste. A suction control device was developed and the effects of suction cycles and suction gradients on the hard clay were investigated. The results showed that the suction gradient had little effect on the suction-water content relation，while the suction cycle has great effect on it，particularly the first cycle of hydration and dehydration. Nuclear magnetic resonance(NMR) method was used to study the water distribution during desaturation. The experimental results showed that the curves gave the evidence of the dependence of water content of the hard clay on the suction. The relationship between the water distribution and the pore size distribution was established. The water content variation during the hydration and dehydration depends on the state of adsorbed water.