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浙江大学学报(工学版)
Journal of ZheJiang University (Engineering Science)  2020, Vol. 54 Issue (12): 2377-2385    DOI: 10.3785/j.issn.1008-973X.2020.12.012
    
Freezing characteristic curve model of saline soil based on generalized Clapeyron equation
Xiang-chuan MENG1,2(),Jia-zuo ZHOU2,*(),Chang-fu WEI1,2,Pan CHEN2,Kun ZHANG3,Zheng-yan SHEN4
1. College of Civil Engineering and Architecture, Guilin University of Technology, Guilin 541004, China
2. State Key Laboratory of Geomechanics and Geotechnical Engineering, Institute of Rock and Soil Mechanics, Chinese Academy of Sciences, Wuhan 430071, China
3. Key Laboratory of Bridge and Tunnel Health Monitoring and Safety Assessment Technology of Gansu Province, Gansu Provincial Transportation Research Institute Co. Ltd, Lanzhou 730030, China
4. School of Mechanics and Civil Engineering, China University of Mining and Technology, Beijing 100083, China
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Abstract  

The unfrozen water mass fraction is the key parameter to evaluate the stability of the soil during the freezing process of saline and coastal areas. The main influencing factors are temperature and salt mass fraction. The differential form of matric suction of frozen soil was obtained by the freezing characteristic curve of salt-free soil, based on the generalized Clapeyron equation considering solute effect, and the Books-Corey model with residual water mass fraction. A theoretical model of soil freezing characteristic curve were derived for frozen soil under arbitrary salt mass fraction and temperature conditions. The freezing test was carried out, and the freezing characteristic curves of silty clay and silt under different water mass fraction and salt mass fraction were obtained by nuclear magnetic resonance. The results show that the mass fraction of unfrozen water decreases exponentially with the reduction of temperature. The unfrozen water mass fraction increases linearly with the increasement of initial solution concentration at the same temperature. The freezing characteristic curves of salt-free soil with different initial water mass fraction are consistent. The silt reaches the residual state more easily than the silty clay. It is verified that the model can predict the freezing characteristic curve of saline soil reasonably by comparing the theoretical model with the test data.

Key words： unfrozen water mass fraction      chemical potential      nuclear magnetic resonance      residual water mass fraction      Clapeyron equation     
Received: 14 October 2019      Published: 31 December 2020
CLC:  TU 445  
Corresponding Authors: Jia-zuo ZHOU     E-mail: xcmeng1994@163.com;jzzhou@whrsm.ac.cn
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Xiang-chuan MENG
Jia-zuo ZHOU
Chang-fu WEI
Pan CHEN
Kun ZHANG
Zheng-yan SHEN
Cite this article:

Xiang-chuan MENG,Jia-zuo ZHOU,Chang-fu WEI,Pan CHEN,Kun ZHANG,Zheng-yan SHEN. Freezing characteristic curve model of saline soil based on generalized Clapeyron equation. Journal of ZheJiang University (Engineering Science), 2020, 54(12): 2377-2385.

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http://www.zjujournals.com/eng/10.3785/j.issn.1008-973X.2020.12.012     OR     http://www.zjujournals.com/eng/Y2020/V54/I12/2377


基于广义Clapeyron方程的含盐土冻结特征曲线模型

未冻水质量分数是评估盐渍土和滨海地区土体冻结过程地层稳定性的关键参数，其主要影响因素为温度和盐的质量分数. 基于考虑溶质效应的广义Clapeyron方程，通过无盐分土冻结特征曲线得到冻土吸力的微分形式，联合考虑残余水的质量分数的Books-Corey模型，推导出在任意盐的质量分数和温度条件下冻土中未冻水质量分数的理论模型. 开展冻结试验，利用核磁共振法获得不同水的质量分数、盐的质量分数下粉质黏土和粉土的冻结特征曲线. 试验结果表明：未冻水质量分数随温度降低呈指数函数递减，在同一温度下未冻水质量分数随着初始溶液浓度的增加近似呈线性增加，不同初始水的质量分数下的无盐土体冻结特征曲线具有一致性，粉土相对于粉质黏土更容易达到残余状态. 将理论模型与试验数据进行对比，验证了该模型能够较为合理地预测含盐土体的冻结特征曲线.


关键词： 未冻水质量分数,  化学势,  核磁共振,  残余水的质量分数,  Clapeyron方程 
土样 土粒相对密度 液限/% 塑限/% 塑性指数 pH 比表面积/（m2·g?1） w砂/% w粉/% w黏/%
粉土 2.73 27.3 15.6 11.7 7.60 16.6 14.6 72.9 12.5
粉质黏土 2.74 36.2 19.4 16.8 7.72 29.9 2.4 74.6 23.0
Tab.1 Physical parameters of experimental soil
Fig.1 Pore size distribution of experimental soil
Fig.2 Experiment equipments and experiment process
Fig.3 Calculation principle of unfrozen water mass fraction
Fig.4 Variation curve of unfrozen water mass fraction with temperature in soils with different salt mass fraction
Fig.5 Comparison of residual water mass fraction in model
Fig.6 Variation curve of unfrozen water mass fraction with temperature in clay with different moisture mass fraction
土样 w0 /% a N wr /% θs /°C
饱和粉土 26.0 0.016 1.1790 2.0 ?0.10
非饱和粉土 15.0 0.022 0.7011 1.9 ?0.08
非饱和粉质黏土 15.0 0.092 0.4000 1.0 ?0.35
Tab.2 Values of sample fitting model parameters
Fig.7 Curve of unfrozen water mass fraction of silt at different temperatures with initial salt mass fraction
Fig.8 Curve of unfrozen water mass fraction of silt at different temperatures with salt mass fraction
Fig.9 Variation curve of unfrozen water mass fraction with temperature in Morin clay with different salt mass fraction
Fig.10 Variation curve of unfrozen water mass fraction of unsalted soil with temperature
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