氯盐粉质黏土冻结过程中变形特性及其机制研究

doi:10.13722/j.cnki.jrme.2021.0525

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摘要近海和海底粉质黏土受海水浸渍形成氯盐土，为研究氯盐粉质黏土冻胀变形特性，揭示其冻胀变形机制，通过开放系统单向冻结试验监测冻结过程中不同氯盐含量土体冻胀变形及水盐迁移规律；开展核磁共振试验获得冻结过程中孔径分布，探讨微观结构变化与宏观冻胀变形内在联系。单向冻结试验结果表明：含盐量对冻结锋面发展、水盐迁移以及冻胀均有显著影响；冻结锋面先快速发展后趋于稳定，含盐量越低冻结锋面稳定位置距离冷端越远。土水势梯度是水盐迁移的驱动力，含盐量越低土水势梯度越大，引起的水盐迁移越明显。冻胀随含盐量增加而减小，补水引起冻胀占总冻胀的主要部分。冻结结束时的冻胀率随含盐量增加表现为先降低后增加，存在一个临界含盐量，即1%含盐量的冻胀率最低。核磁共振试验表明：试样中的孔隙主要由中孔隙组成，冻结过程中中孔隙向大孔隙和小孔隙转化，含盐量越低孔隙体积转化比例越大。这是由于低含盐量土中发生更多冰水相变，微观孔隙结构改变更为明显，产生冻胀也更为显著。

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	刘健鹏1
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	杨平1
	赵记领1

关键词 ：土力学, 氯盐粉质黏土, 冻结过程, 冻胀变形, 水盐迁移, 孔径分布

Abstract：The offshore and seabed silty clays are typical chloride saline soils since they are soaked in seawater. This paper aims at characterizing the frost heave mechanism of chloride silty clay. A series of open-system one-dimensional frost heave tests were conducted on chloride silty clay to investigate the frost heave and water-salt migration during freezing. The Nuclear Magnetic Resonance(NMR) relaxometry tests were performed to obtain the pore-size distribution of specimens at a specific time of interest during freezing. The internal relationship between microstructure change and frost heave was discussed. The results of open-system one-dimensional frost heave tests indicated that the propagations of freezing front，water-salt migration and frost heave were dependent on the salt content. The freezing front quickly developed，moved at a high rate and then gradually stabilized. The location of the freezing front at the thermal equilibrium was farther away from the cold end in a lower-salt content specimen. The water potential gradient was higher in lower-salt content specimen，driving more water-salt migration. The frost heave decreased with increasing the salt content and the solution intake induced frost heave dominated in the total frost heave. At the end of freezing process，the frost heave ratio increased and then decreased with increasing the salt content. It was found out that a threshold(i.e.，1% salt content) existed，at which the minimal frost heave ratio could be identified. The NMR results indicated that mesopores account for the main part of specimen voids and mesopores transformed into macro- and micropores during freezing. The lower the salt content，the greater the transformation ratio of the pore volume. For that more amount of water-ice phase change can be identified in low-salt content specimen，leading to more significant microstructure change. Consequently，the specimen with lower salt content experienced a larger amount of frost heave.

Key words： soil mechanics chloride silty clay freezing process frost heave water-salt migration pore size distribution

引用本文:

刘健鹏1，2，杨平1，赵记领1. 氯盐粉质黏土冻结过程中变形特性及其机制研究[J]. 岩石力学与工程学报, 2022, 41(8): 1689-1700.
LIU Jianpeng1，2，YANG Ping1，ZHAO Jiling1. Deformation properties of chloride silty clay during freezing. , 2022, 41(8): 1689-1700.

链接本文:

http://rockmech.whrsm.ac.cn/CN/10.13722/j.cnki.jrme.2021.0525 或 http://rockmech.whrsm.ac.cn/CN/Y2022/V41/I8/1689

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