基于核磁共振技术的岩石孔隙结构冻融损伤试验研究

EXPERIMENTAL STUDY OF ROCK POROUS STRUCTURE DAMAGE CHARACTERISTICS UNDER CONDITION OF FREEZING-THAWING CYCLES BASED ON NUCLEAR MAGNETIC RESONANCE TECHNIQUE

为研究岩石在冻融循环作用下的孔隙结构损伤特性,选取寒区花岗岩为岩样,在冻结温度为-40℃,融解温度为20℃条件下,分别进行3轮冻融循环试验,并对每轮冻融循环后的岩样进行核磁共振(NMR)测量,得到同一块岩样不同冻融循环次数后的孔隙度、横向弛豫时间T2分布及核磁共振图像(NMRI)。结果表明:花岗岩的T2分布主要为3个峰,随着冻融循环次数的增多,岩石的孔隙度、核磁共振T2谱分布和T2谱面积均会增大,但每个岩样的增大幅度均不同,反映出冻融循环作用下岩石中孔隙的发育和扩展特性;核磁共振图像显示同一块岩样在不同冻融循环次数后的内部微观结构分布,动态地显示岩石的冻融损伤过程。冻融循环条件下岩石核磁共振特征为岩石冻融损伤机制研究提供可靠的试验数据。

For the purpose of researching the damage characteristic of rock porous structure under the condition of freezing-thawing cycles,taking the granite as the samples,3 times freezing-thawing cycles experiments with the freezing temperature of-40 ℃ and thawing temperature of 20 ℃ were conducted.The nuclear magnetic resonance（NMR） technique was used to test the rock samples;and the rock porosity,crosswise relaxation time T2 distribution and nuclear magnetic resonance imaging（NMRI） were obtained.The results show that T2 distribution of granite exhibits three peaks.Rock porosity,T2 distribution and T2 spectrum area increase with the freezing-thawing cycles.The variation ranges of them are different for every sample and it indicates that the characteristics of rock porous grow and expand under the condition of freezing-thawing cycles.Also,the microstructure distributions of porous have been visually shown by the NMRI;and the processes of rock damage under the condition of freezing-thawing cycles have been shown dynamically.The NMR characteristics of rock under the condition of freezing-thawing cycles has provided reliable experimental data for research of rock damage mechanism.