处置库工程屏障系统的自封闭机理及其缓冲性能

项目名称： 处置库工程屏障系统的自封闭机理及其缓冲性能

项目编号： No.40802069

项目类型： 青年科学基金项目

立项/批准年度： 2009

项目学科： 建筑科学

项目作者： 陈宝

作者单位： 同济大学

项目金额： 20万元

中文摘要： 本课题以高放废物处置库工程屏障中的粘土屏障材料为对象，研究了不同压缩应力状态下粘土体积变形的微观特征、密实度和吸力及渗压梯度对渗透特性的影响、具有不连续面的高压实膨润土的膨胀渗透性能及其微观机理、高碱环境中高压实膨润土膨胀渗透特性、以及粘性土的热传导特性等。主要结论有：1、粘土中的孔隙可分为大孔隙、中孔隙、小孔隙和微孔隙，小孔隙占据大部分空间，在各向等压状态下土颗粒发生空间平移使颗粒间变得更为紧密，在K0压缩状态下土颗粒发生旋转使孔隙变得扁平；2、非饱和土的渗透性与其所承受的应力、渗压梯度和基质吸力都有着密切的联系；3、接缝的存在将导致膨润土的膨胀力减小、渗透性增大，从而降低了膨润土在处置库中的自封闭性能；4、在碱溶液入渗作用下，膨润土内部的孔隙率增大，蒙脱石含量减少,进而提高了膨润土的长期渗透性，导致膨润土的封闭和缓冲性能降低；5、饱和粘土的孔隙比越大其热导率越小，随着含水率从饱和状态逐渐降低，初期土样会出现明显体积收缩、热导率升高，而后当含水率降到低于塑限的时候，土样体积收缩速率明显变缓，热导率则逐渐降低。上述研究成果对于我国高放废物地质处置中工程屏障系统设计和建设具有参考价值。

中文关键词： 高放废物处置；工程屏障；体积变形；渗透性；热导率

英文摘要： Concerning the clayey material of engineered barrier for the geological displosal of high-level radioactive waste, this project was carried out on the microstructural characteristics of volumetric deformation of clay under different compression stresses; hydraulic conductivity of unsaturated material under different density, suction (water content) and hydraulic pressure; influence of joints on the self-sealing behaviour of highly compacted bentonite; microscopic pore structure of compacted bentonite submitted to hyper-alkaline solution; thermal conductivity of clayey material and so on. Some main conclusions as follows: 1. The pores in clay can be divided into macropore, mesopore, fine pore and micropore; where the fine pores account most on the volumetric deformation of clay, under the isotropic compression state the soil particles move and get closer to each other with the development of compression, while under the K0 compression state the soil particles rotate and the pores become flat; 2. The permeability of unsaturated clayey material has close relationships with confined stress, hydraulic pressure and matrix suction; 3. The existence of joints causes swelling pressure decreased, permeability increased and thus reduces the self-sealing performance of bentonite in the engineered barrier of repository; 4. The infiltration of hyper alkaline solution increases the porosity and decreases the smectite content in bentonite, which leads to the alteration of montmorillonite and porosity, amplifying the permeability, and resulting in a weak ability of sealing and buffering; 5. The thermal conductivity of saturated clay decreases with the void ratio; when the water content drops down gradually from saturated value to dry value, the soil sample shrinks evidently firstly and its thermal conductivity increases; while the water content drops down to near the plasticity limit, the volumetric shrinkage becomes stable and the thermal conductivity reachs its maximum value. The results achieved may be good reference to the design and construction of the Chinese repository in future.

英文关键词： Geological disposal of high level radioactive waste; Engineered barriers; Volumetric deformation; Permeability; Thermal conductivity