摘要
膨润土缓冲材料热传导特性的研究,对于高放废物深地质处置系统的安全评价至关重要。基于串、并联原理,通过将土体孔隙划分为与固相基质并联和串联两部分,提出了考虑矿物成分、颗粒亲水性、孔隙率及饱和度等因素的非饱和膨润土有效热传导系数的4种预测形式,建立了基于4种形式线性组合的有效热传导特性预测模型。详细讨论了模型参数的确定方法,并讨论了孔隙率、饱和度和孔隙结构、颗粒亲水性等因素对土体有效热传导特性的影响。基于MX-80膨润土和高庙子膨润土热传导特性试验成果,对模型的预测性能进行了验证。结果表明,由于膨润土颗粒尺寸较小且具有亲水特性,孔隙内的空气与水宜采用并联描述。研究成果对于非饱和膨润土的导热性能以及工程屏障系统的THM耦合数值模拟研究具有一定的参考价值。
Bentonites have been widely adopted as the bufferlbackfill materials for repositories of high-level radioactive waste disposal. Characterization of the effective thermal conductivity of the buffer materials is of great importance for optimization design and safety assessments of the repositories. Using the concept of the series-parallel structural models, the porosity of soils is decomposed into two components： one in parallel and the other in series connected to the solid phase. An effective structure depends on the decomposition is introduced to describe the heat transfer process of the porous soils considering the structural connections of pores and the solid phase. On this basis, four formulas which represent different series-parallel arrangements of pore fluids （water and air mixture） are proposed to predict thermal conductivity of unsaturated soils with a comprehensive consideration of the effects of mineralogical composition, porosity and saturation. An effective model for thermal conductivity of unsaturated soil is then developed based on a linear composition of the four formulas. Parameterization of the model is discussed; and the behaviors of the model with respect to the variations in porosity and saturation are illustrated. The model is validated against experimental data of thermal conductivity of MX-80 and Gaomiaozi bentonites. The results show that the arrangement of air and water in the pores tended to be in parallel connection for unsaturated bentonites because of the fine size and wettability of the soil particles. This research may provide a helpful reference for predicting thermal conductivity of unsaturated bentonites and numerical modeling of the coupled thermo-hydro-mechanical （THM） processes in the engineered barrier systems.
出处
《岩土力学》
EI
CAS
CSCD
北大核心
2014年第4期1041-1048,1055,共9页
Rock and Soil Mechanics
基金
国家优秀青年科学基金项目(No.51222903)
国家自然科学基金面上项目(No.51179136
No.51079107)
关键词
非饱和土
有效热传导系数
高放废物地质处置
膨润土
unsaturated soil
coefficient of effective thermal conductivity
high-level radioactive waste disposal
bentonite
