硫酸钠溶液在降温结晶过程中的盐胀与冻胀  

Saline expansion and frost heave of sodium sulfate solution during cooling crystallization process

作　　者：李星星[1,2] 王思敬[1] 肖锐铧[1] 程东幸[3] 严福章[4] LI Xing-xing WANG Si-jing XIAO Rui-hua CHENG Dong-xing YAN Fu-zhang(Key Laboratory of Shale Gas and Geocngineering, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China University of Chinese Academy of Sciences, Beijing 100049, China Northwest Electric Power Design Institute Co., Ltd of China Power Engineering Consulting Group, Xi＇an 710075, China State Power Economic Research Institute, Beijing 102209, China)

机构地区：[1]中国科学院地质与地球物理研究所中国科学院页岩气与地质工程重点实验室,北京100029 [2]中国科学院大学,北京100049 [3]中国电力工程顾问集团西北电力设计院有限公司,陕西西安710075 [4]国网北京经济技术研究院,北京102209

出　　处：《岩土工程学报》2016年第11期2069-2077,共9页Chinese Journal of Geotechnical Engineering

基　　金：科技部支持计划课题(2014BAK16B02);国家电网公司科技项目(41560950);博士后科学基金项目(2014M550837)

摘　　要：在降温过程中,硫酸钠溶液溶解度降低,硫酸钠结晶析出。当温度降低到一定温度时,除硫酸钠结晶外,溶液中的水也结晶析出。溶液在孔隙中的结晶是导致孔隙介质变形与破坏的主要原因。为探明孔隙介质中溶液结晶导致孔隙介质变形与破坏机理,构建了Na_2SO_4+H_2O二元体系在降温结晶过程中的体积变化率计算方法。该方法依据Na_2SO_4+H_2O二元体系中各相态的平衡浓度计算各相态在不同温度下的含量,进而根据该温度条件下溶液及晶体体积计算体系的体积变化。计算结果与前人试验结果比较发现,计算方法能很好地预测Na_2SO_4+H_2O二元体系在平衡态转化过程中盐胀与冻胀量。此外,在降温冻结过程中,盐胀率远远小于冻胀率;当晶体为Na_2SO_4·7H_2O时,盐胀阶段的体积增长率较小,而冻胀阶段体积急剧增长。During cooling process, solubility of sodium sulfate decreases, and part of sodium sulfate in the solution precipitates and crystallizes. When the temperature is lower than the specific temperature, in addition to crystallization of sodium sulfate, liquid water also precipitates as ice. The crystallization of the aqueous solution in porous medium induces the deformation and failure of porous medium, such as saline expansion and frost heave deformation of saline soils with sulfate sodium, salt efflorescence of wall painting, degradation of stone and concrete, etc. To study the deformation and failure mechanism of porous medium with saline solution during cooling process, the method for calculating the volumetric change rate of the system of Na_2SO_4＋H_2O during cooling process is proposed. In the procedure of calculation, the content of phases is determined according to the equilibrium concentration of phases in the system, Na_2SO_4＋H_2O, and the volume of the phases is added to calculate volumetric change rate of the system. Compared with the existing tests, the proposed method can successfully predict the volumetric change rate. The saline expansion rate is smaller than frost heave rate during cooling process. In addition, when heptahydrate sodium sulfate crystallizes and precipitates during at the saline expansion stage, the volumetric change ratio is relatively small, but the volumetric change abruptly increases at the frost heave stage.

关 键 词：硫酸钠溶液 温度 结晶 盐胀 冻胀 

分 类 号：TU43[建筑科学—岩土工程]