干湿循环对不同密度砂岩强度劣化的影响

Effect of Dry-Wet Cycles on the Deterioration of Sandstone with Various Initial Dry Densities

揭示干湿循环过程中砂岩强度的劣化规律对防治失稳岩质边坡具有重要指导意义.以兰州市岩质边坡的砂岩为研究对象,通过抗压、抗拉试验及电镜扫描观察,分析干湿循环对不同初始干密度砂岩强度的劣化影响.研究结果表明,砂岩的单轴抗压强度、弹性模量、抗拉强度及其劣化速率与干湿循环次数成负相关,单轴抗压强度、弹性模量和抗拉强度与干湿循环次数具有良好的指数关系.同一强度参数中,不同初始干密度砂岩强度参数值的差别随干湿循环次数的增加呈减小趋势.干湿循环次数相同时,随初始干密度的增大,单轴抗压强度、弹性模量和抗拉强度及其劣化程度呈递增趋势.在干湿循环递进的过程中,砂岩的微观结构发生显著改变,不同初始干密度砂岩的微观结构差别逐渐减小.干湿循环对砂岩强度的劣化与循环次数和初始干密度密切相关.

Revealing the deterioration law of sandstone strength under dry-wet cycles is highly significant for preventing and controlling unstable rocky slope of road engineering.Taking sandstone of a rocky slope in Lanzhou city as the research object,the effects of dry-wet cycles on the deterioration of sandstone with various initial dry densities were analyzed by uniaxial compressive test,tensile test and SEM observation.The results show that the uniaxial compressive strength,elastic modulus,uniaxial tensile strength and their deterioration rate of sandstone are ne-gatively correlated with cycle number.The uniaxial compressive strength,elastic modulus and uniaxial tensile strength are respectively in good exponential correlation with cycle number.Among the same strength parameters,the difference in strength values of sandstone for various initial dry densities decreases with the increase of cycle number.The uniaxial compressive strength,elastic modulus,uniaxial tensile and their total deterioration degree gradually increase with the increase of initial dry density when cycle number is the same.During the increase of cycle number,the microstructure of sandstone changes significantly,and the microstructure difference between sandstone with various initial dry densities decreases gradually.Hence,the effects of dry-wet cycles on sandstone strength are related to cycle number and initial dry density closely.