【摘要】 为了研究不同水化环境下的砂岩经多次冻融循环后的损伤情况,将饱和蒸馏水与3%NaCl水溶液的砂岩试样,在冻结温度为-30℃、融化温度30℃的环境下进行循环冻融试验;并同步采集冻融中的声发射信号,每3次冻融循环后进行1次低场核磁分析与光学显微观测,在冻融循环结束后再进行单轴压缩试验。试验结果表明:蒸馏水环境和3%NaCl溶液环境作用下,随着冻融循环次数的增加,砂岩试样的T₂谱向右偏移、T₂谱总面积增加、孔隙度增加、内部显微结构破坏,且3%NaCl溶液冻融组变化更为严重;循环冻融后砂岩的单轴压缩声发射绝对能量概率密度依然满足幂定律分布,但临界指数增加,而3%NaCl循环冻融组的增量更大;每次冻融循环过程中,随着循环次数的增加,声发射概率密度的临界指数表现为先增加后降低,与已有的超声波检测试验结果相一致,而融化过程的临界指数峰值超前于结冻过程,冻融损伤主要是因静压、渗透压破坏以及水化介质对岩石的溶解、侵蚀造成的。本研究将为寒区岩体工程损伤破坏机制和稳定性评价提供一定的参考价值。更多还原

【Abstract】 To study the damage of sandstone in different hydration environment conditions after repeated freeze-thaw cycles, saturated freezing and thawing experiments were carried out on sandstone samples under the freezing temperature of -30 ℃ and melting temperature of 30 ℃. The acoustic emission（AE） signals were recorded during each freezing-thawing cycle, and the microscopic characteristics of sandstone were investigated by low field nuclear magnetic resonance（NMR） and an optical microscope after every three cycles. The uniaxial compression test was conducted at the end of cycles. The results show that since 3% NaCl solution leads to the internal microstructure destruction, with increasing cycle index, the T₂ spectrum shifts to the right, the total area of T₂ spectrum and the porosity increase. The AE absolute energy probability density of sandstone still meets the power law distribution after freeze-thaw cycle under uniaxial compression, but the critical exponent increases and the increment of 3% NaCl is greater than that of distilled water. In addition, the critical exponent of AE probability density for each freezing and thawing cycle increases first and then decreases with increasing cycle number, which is similar to existing ultrasonic testing results. The peak of critical exponent in thawing process is higher than that in freezing process, which means that thawing process has shorter breaking time and a lower damage degree. The freeze-thaw damage is mainly caused by the static pressure, osmotic pressure destruction and dissolution but also the erosion of rock by hydration medium. This study can provide some references for understanding failure mechanism and stability evaluation of rock engineering in cold regions.更多还原