冻融作用下炭质页岩微结构损伤特性研究

Research on Damage Characteristic of Carbonaceous Shale Micro-structure Under the Influence of Freezing-thawing Cycles

通过核磁共振(NMR)试验分析冻融循环作用下炭质页岩的T2谱分布、孔隙度、T2谱面积的变化,利用超声波检测分析冻融循环作用下炭质页岩纵波波速的变化,引入损伤变量探讨炭质页岩冻融损伤与循环次数的关系,建立了炭质页岩冻融损伤演化方程。结果表明,随冻融次数的增多,炭质页岩T2谱分布、T2谱面积及孔隙度均逐渐增大,纵波波速在不断衰减;当冻融循环次数达400次时,炭质页岩微结构损伤度达到最大值。

Through nuclear magnetic resonance （NMR） test, the variations of the Tz spectrum distribution,the porosi ty and the T2 spectral area of carbonaceous shale were analyzed under the freezeing-thawing cycles. Corresponding change of the longitudinal wave velocity of carbonaceous shale was investigated by virtue of the ultrasonic testing. A damage vari able was introduced to study the relationship between the freezeing thawing damage and the cycle number,and the evolu tion equation of carbonaceous shale was then established. The experimental results show that, with the increase of the number of freezeing-thawing cycles,the distribution of T2 spectrum,the area of T2 spectrum and the porosity of carhona ceous shale gradually increase, while the longitudinal wave velocity continuously decreases. The micro-structure damage degree of carbonaceous shale reaches the maximum value when the number of freezeing-thawing cycles is up to 400 times.