高压实高庙子膨润土非饱和蠕变特性及其本构模型研究

During the long-term operation of the high-level radioactive waste repository, bentonite, as the buffer/backfill materials, will submit to the unsaturated creep deformation, which leads to the subsidence of the waste canister, weakening the protection function of the waste repository. The highly compacted Gaomiaozi (GMZ) bentonite is chosen as the research subject in this project. The osmotic technique is adopted to extend the suction control range of the unsaturated high pressure oedometer. Suction control in a full range is realized in the unsaturated creep tests. With the improved unsaturated high pressure oedometer, unsaturated creep tests were conducted on GMZ bentonite and the creep coefficients were obtained. Effects of suction and vertical stress on the creep behavior of GMZ bentonite were investigated. Based on the basic principle of unsaturated soil mechanics and reology mechanics of rock and soil materials, a creep constitutive model with suction effect considered was established for the GMZ bentonite to realize the analysis of the mechanism of creep behavior of GMZ bentonite. The results obtained in this project are of great importance to the research of the long-term coupling behavior of the buffer/backfill materials, to the development of theory of unsaturated soil mechanics and reology mechanics and to the choice and design of buffer material of deep geological repository of the high-level radioactive waste in China.

在高放废物处置库长期运营过程中，作为缓冲/回填材料的膨润土将发生非饱和蠕变，导致处置库中废物罐下沉，削弱了处置库的屏障作用。针对该问题，本项目拟以高压实高庙子（GMZ）膨润土为研究对象，借助渗析法吸力控制技术，拓展既有非饱和高压固结仪的吸力控制范围，实现非饱和蠕变试验的全吸力范围控制；采用改进的非饱和高压固结仪，开展高压实高庙子（GMZ）膨润土非饱和蠕变试验，获取相关蠕变参数，分析吸力、竖向应力对高压实GMZ膨润土蠕变特性的影响；在此基础上，运用非饱和土力学及岩土流变力学的基本理论，构建适用于高压实GMZ膨润土的非饱和蠕变本构模型，实现高压实GMZ膨润土蠕变特性的机理分析。预期成果对于缓冲/回填材料的长期性能研究，丰富非饱和土力学和流变力学理论及指导我国在核废料深地质处置中缓冲材料的选择与工程实践等，均具有重要的理论与工程实际意义。

以核废料深地质处置缓冲/回填材料为研究对象，对高压实高庙子（GMZ）膨润土开展了一系列吸力控制条件下的非饱和蠕变试验和膨胀特性时效性试验，分析了吸力、竖向应力对试样蠕变特性的影响以及静置时间对膨胀特性的影响；蠕变试验结果表明吸力降低和竖向应力增大会加剧试样的蠕变变形，膨胀特性试验表明试样膨胀性能随静置时间的增长不断衰减，且前期衰减速率较快，后期较慢，静置30天后趋于稳定。建立了反映应力-吸力-时间相互耦合的高压实GMZ膨润土非饱和蠕变经验模型，次固结压缩系数和压缩系数的比值与吸力的对数呈线性关系，该结论对于研究缓冲/回填材料在地下水作用下的长期变形提供了一定参考。