Abstract：The freezing of pore water is the root of frost heave damage of rock mass in cold regions. Studying the evolution law of unfrozen water content is of great significance to understand the freezing process of pore water and to reveal the damage mechanism of frozen rock mass. Taking intact and double fractured sandstone as the research object，the cyclic freeze-thaw tests were carried out at different freezing temperatures(－2 ℃，－5 ℃，－10 ℃，－15 ℃，－20 ℃)，and the changes of the unfrozen water content were detected by nuclear magnetic resonance(NMR) system. By analyzing the influence of freezing temperature，freeze-thaw times and cracks on unfrozen water，the relationship between the unfrozen water content and the sandstone meso damage is explored. The results show that：(1) The unfrozen water content of rock samples decreases exponentially with the decrease of the temperature. Under the action of the temperature gradient，the freezing rate of capillary water is the fastest，followed by free water，and the freezing rate of bound water is the slowest. (2) The unfrozen water content has a linear negative correlation with the number of freeze-thaw cycles. When the freezing temperature is lower than －20 ℃，the influence of the number of freeze-thaw on the unfrozen water content is weakened，but the existence of accelerates the freezing rate of free water in the early stage of freezing and thawing，and the freezing of combined water in the middle and late stages. Compared with the complete rock sample，the unfrozen water content of fractured rock sample is reduced by 5%. (3) The pore volume and permeability of rock are positively correlated with ice content. The freeze-thaw damage of fractured rock is mainly caused by the in-situ freezing of free water in the early stage of freeze-thaw，the continuous freezing of bound water in the later stage and the migration of capillary water. This study is helpful to understand the freeze-thaw characteristics of fractured rocks，and provides a theoretical basis for the safe construction and operation of rock mass engineering in cold regions.
宋勇军，张 君，陈佳星，郭玺玺，孟凡栋，李晨婧. 裂隙砂岩未冻水含量演化特征研究[J]. 岩石力学与工程学报, 2023, 42(3): 575-584.
SONG Yongjun，ZHANG Jun，CHEN Jiaxing，GUO Xixi，MENG Fandong，LI Chenjing. Study on evolution characteristics of unfrozen water content in fractured sandstone. , 2023, 42(3): 575-584.
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