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研究岩石在低温冻结过程中细观结构的变化和孔隙(裂隙)水的冻结过程,对于深化认识冻结岩石的力学及损伤特性具有重要意义。通过开展不同冻结温度下岩石细观结构CT扫描实验,获得了岩样在20℃,-2℃,-5℃,-10℃,-20℃,-30℃时细观结构的CT图像。采用Canny算子对冻结岩石CT图像进行边缘检测,完成了冻结过程中岩石二维细观结构的识别。基于体视学理论,提出表征冻结岩石细观结构特征参数的计算公式,分析了孔隙(裂隙)水冻结过程中岩石细观结构的变化,实现了冻结过程中岩样不同截面裂隙(孔隙)的长度、宽度、面积及圆形度等参数变化规律的定量分析。分析结果表明:在0℃~-2℃区间,岩样扫描层面内裂隙(孔隙)的长度、宽度、面积快速增加,这一阶段为宏观裂隙中体积水结冰阶段,裂隙(孔隙)的扩张由体积膨胀机制引起;在-2℃~-5℃区间,裂隙(孔隙)的扩张速率明显降低,该阶段为细观(部分微观)裂隙(孔隙)中水的结冰过程;在-5℃~-20℃区间,裂隙(孔隙)的扩张速率又开始增加,但低于0℃~-2℃区间的增加速率,该阶段为微观裂隙(孔隙)中的水向冰晶体迁移阶段,由分凝冰机制引起裂隙的扩张。
Studying the change of mesostructure and the freezing process of pore (fissure) water during low temperature freezing is of great significance to deepen the understanding of mechanics and damage characteristics of frozen rock. By carrying out CT scanning experiments of rock mesostructures under different freezing temperatures, the CT images of the mesostructures of the rock samples at 20 ℃, -2 ℃, -5 ℃, -10 ℃, -20 ℃ and -30 ℃ were obtained. The Canny operator is used to detect the frozen rock CT image and the identification of the two-dimensional mesoscopic structure of the rock during the freezing process is completed. Based on stereological theory, a formula to characterize the microscopic structure parameters of frozen rock is proposed. The changes of rock mesoscale structure during the freezing process of pore water are analyzed, and the fractures (pores) Length, width, area and circularity and other parameters of the quantitative analysis. The results show that the length, width and area of fractures (pores) in the scanning planes of rock samples rapidly increase from 0 ℃ to -2 ℃ in this period, which is the stage of volume water icing and the expansion of fractures (pores) in macro-fractures Which is caused by the volume expansion mechanism. The expansion rate of fissures (pores) obviously decreases in the range of -2 ° C to -5 ° C, which is the icing process of water in the fissures (pores) ~ -20 ℃, the expansion rate of fissure (pore) begins to increase again, but it is lower than the increasing rate of 0 ℃ ~ -2 ℃, which is the migration stage of water in micro fissure (pore) to ice crystal. Frozen ice mechanism caused by the expansion of cracks.