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| Study on damage mechanisms of the microstructure of sandy conglomerate at Maijishan grottoes under freeze-thaw cycles |
| YANG Hongrui1，LIU Ping1，2，SUN Bo1，3，YI Zhiyi1，WANG Jiajie1，YUE Yongqiang4 |
(1. College of Civil Engineering and Mechanics，Lanzhou University，Lanzhou，Gansu 730000，China；2. Key Laboratory of Mechanics on Disaster and Environment in Western China，Ministry of Education，Lanzhou University，Lanzhou，Gansu 730000，China；
3. Northwest Research Institute Co.，Ltd. of CREC，Lanzhou，Gansu 730000，China；4. Study on the Art of Maiji Mountain Grottoes，Lanzhou，Tianshui 741000，China) |
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Abstract The freeze-thaw cycle is one of the main reasons affecting the weathering of Maijishan grottoes. The changes of the wave velocity、the mass and the tensile strength of the saturated sandy conglomerate under open conditions due to freeze-thaw cycles are studied through laboratory experiments in 3 temperature ranges of －5 ℃–20 ℃，－10 ℃–20 ℃ and －15 ℃–20 ℃，and CT and digital image processing techniques are used to analyze the changes of the microstructure characteristics of the rock samples. The concept of homogenized stress is introduced and compared with the macromechanical properties of the rock as a criterion for whether the rock is damaged. The results show that the mass，the wave velocity and the tensile strength are inversely proportional to the number of freeze-thaw cycles but directly proportional to the minimum temperature of the freeze-thaw cycle. It is proposed that the temperature range is the key environmental control factor for the freeze-thaw degradation of rock，and the destruction of the original cement structure of the rock and the pores are the key internal factor. The comparison between the crystallization homogenization stress and the rock yield strength can be better used to judge the influence of freezing and thawing on rock damage. The research results are expected to provide a theory for the research and development of freeze-thaw weathering mechanisms of stone cultural relics and related protection technologies.
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2021, Vol. 40 
