摘要
碱-热条件下膨润土缓冲层材料的导热性能是核废物深地质处置库设计的一个关键因素。对MX80膨润土粉末进行不同碱-热工况预处理,采用热针法探讨碱-热条件下膨润土缓冲材料导热系数的演化规律;选取代表试样分别进行X射线衍射(XRD)、扫描电镜(SEM)、压汞(MIP)和热重分析(TGA)等试验,揭示出碱-热作用对膨润土试样矿物成分、微观形貌、孔隙结构和结合水形态等演化特征的影响机制,阐释碱-热条件下膨润土缓冲材料导热系数演化的微观机理。试验结果表明:碱-热条件下,膨润土试样的导热系数λ随碱液p H值的递增而减小,随环境温度T的升高而增大,在高碱性溶液(pH=13.0~14.0)和高温环境(T=60℃~90℃)中这一特性表现得尤为显著;根本原因在于试样中原有矿物成分在碱液作用下发生不同程度的溶蚀现象,表现为蒙脱石和石英含量的减少、方沸石含量的增加,导致试样中固体成分减少、孔隙率增加、表观干密度减小、吸水性能变弱,而环境温度在该过程中起到良好的促进作用。
The evolution characteristics of thermal conductivity of the bentonite as buffer layer materials under alkaline-thermal conditions are a key factor in the conceptual design of a deep geological repository for nuclear waste.The evolution laws of thermal conductivity of the bentonite buffer materials under alkaline-thermal conditions are investigated by using the thermal probe method for MX80 bentonite powder pretreated under different alkaline-thermal conditions.On this basis,the XRD,SEM,MIP and TGA tests are carried out on the representative specimens to reveal the mechanisms of alkaline-thermal effects on the evolution of mineral composition,microscopic morphology,pore structure and water-binding morphology of bentonite samples,and to further elucidate the microscopic mechanisms of the evolution of thermal conductivity of bentonite buffer materials under alkali-thermal conditions.The test results show that under alkali-thermal conditions,the thermal conductivity(λ)of the bentonite samples decreases with the increasing pH value of the alkaline solution and increases with the increasing ambient temperature(T).This characteristic is particularly significant in highly alkaline solutions(pH=13.0~14.0)and high temperature environments(T=60℃~90℃).The underlying cause is the dissolution of the original mineral components in the samples under the action of alkaline solution to varying degrees,as evidenced by the reduction in the contents of montmorillonite and quartz and the increase in the zeolite content,resulting in reduction in the solid content of the samples,increase in the porosity,and reduction in the dry density and water absorption properties,while the ambient temperature plays a good role in facilitating the process.
作者
曾召田
林铭宇
孙德安
曹珊珊
车东泽
梁珍
ZENG Zhaotian;LIN Mingyu;SUN De’an;CAO Shanshan;CHE Dongze;LIANG Zhen(Guangxi Key Laboratory of Geotechnical Mechanics and Engineering,Guilin University of Technology,Guilin 541004,China;Department of Civil Engineering,Shanghai University,Shanghai 200444,China)
出处
《岩土工程学报》
EI
CAS
CSCD
北大核心
2024年第7期1408-1417,共10页
Chinese Journal of Geotechnical Engineering
基金
广西自然科学基金项目(2023GXNSFAA026187)
国家自然科学基金项目(41962014,42167020)。
关键词
膨润土缓冲材料
导热系数
碱-热条件
演化特征
微观机制
bentonite buffer material
thermal conductivity
alkaline-thermal condition
evolution characteristic
micromechanism
