Abstract For engineering projects in cold regions, the failure behaviour of jointed rocks is affected by freeze–thaw (F-T) cycle action. To reveal the fracture characteristics of rock under the influence of cyclic F-T treatments, fracture tests on semicircular specimens with different F-T cycle numbers were conducted. The fracture toughness values in different modes were investigated by SCB specimens with different crack inclinations (0°, 5°, 15°, 30°, 45° and 54°). The experimental results show that cyclic F-T treatments can lead to degradation in three kinds of fracture toughness values. Specifically, the value of KIC (fracture toughness in mode I) decreases by 3.1, 7.2, 15.0 and 24.3% after 20, 40, 60, and 80 F-T cycles, respectively. When the number of cycles increases from 20 to 80, the value of KIIC (fracture toughness in mode II) of the sandstone decreases by 8.43, 12.0, 18.8 and 27.9%. For the specimen with crack inclinations of β = 5°, 15°, 30° and 45°, after 80 F-T cycles, the Keff (effective fracture toughness) value decreases to approximately 83.7, 78.3, 79.1 and 76.7% of the initial value, respectively. The mixed-mode fracture toughness ratios Keff/KIC were calculated and compared with the theoretical solution. The experimental results of Keff/KIC agree well with the theoretical results calculated based on the MMTS criterion. Moreover, after F-T treatments, the fracture paths of the SCB specimens are more tortuous than those in specimens without F-T treatment. In addition, the fracture surface morphological characteristics of the SCB specimen were obtained by a 3D laser scanner. Overall, the fractal dimension value increases gradually with additional F-T cycles. This indicates that the F-T treatments lead to rough fracture paths and fracture surfaces.

中文翻译：

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循环冻融处理对不同裂缝模式下砂岩裂缝特征的影响：室内试验

摘要 对于寒冷地区的工程项目，节理岩的破坏行为受冻融循环作用的影响。为了揭示岩石在循环 FT 处理影响下的断裂特征，对不同 FT 循环次数的半圆形试样进行了断裂试验。采用不同裂纹倾角（0°、5°、15°、30°、45°和54°）的SCB试样研究了不同模式下的断裂韧性值。实验结果表明，循环 FT 处理会导致三种断裂韧性值的降低。具体而言，在 20、40、60 和 80 次 FT 循环后，KIC（模式 I 中的断裂韧性）值分别下降了 3.1、7.2、15.0 和 24.3%。当循环数从 20 增加到 80 时，砂岩的 KIIC（模式 II 断裂韧性）值分别下降 8.43、12.0、18.8 和 27.9%。对于裂纹倾角为 β = 5°、15°、30° 和 45° 的试样，经过 80 次 FT 循环后，Keff（有效断裂韧性）值下降到初始值的大约 83.7、78.3、79.1 和 76.7%，分别。计算混合模式断裂韧度比 Keff/KIC 并与理论解进行比较。Keff/KIC 的实验结果与基于 MMTS 准则计算的理论结果非常吻合。此外，经过FT处理后，SCB试样的断裂路径比未经FT处理的试样更曲折。此外，SCB 试样的断口形态特征是通过 3D 激光扫描仪获得的。全面的，随着额外的 FT 循环，分形维数值逐渐增加。这表明 FT 处理导致粗糙的断裂路径和断裂表面。