NMR research on deterioration characteristics of microscopic structure of sandstones in freeze-thaw cycles

砂岩细观结构冻融损伤特征的核磁共振研究（英文）

In order to study the deterioration characteristics of the microscopic structure of sandstones in freeze-thaw cycles, tests of180 freeze-thaw cycles were performed on sandstone specimens. The nuclear magnetic resonance （NMR） technique was applied tothe measurement of sandstone specimens and analysis of the magnetic resonance imaging. Then, the fractal theory was employed tocompute the fractal dimension values of pore development of rocks after different freeze-thaw cycles. The results show that the massand porosity of rocks grow with the increase of freeze-thaw cycles. According to the NMR T2 distribution of sandstones, the poresizes of rock specimens increase after 180 freeze-thaw cycles, especially that of the medium-sized and small-sized pores. The spatialdistribution of sandstone pores after freeze-thaw cycles has fractal features within certain range, and the fractal dimension ofsandstones tends to increase gradually.

为了研究砂岩细观结构的冻融损伤特性,对砂岩共进行了180次冻融循环实验,利用核磁共振技术(NMR)对冻融循环后的岩样进行了检测和核磁共振成像分析,并采用分形理论计算了砂岩经历不同冻融循环后孔隙发育的分形维数。研究结果表明:随着冻融循环次数的增多,砂岩的质量、孔隙度、核磁共振弛豫时间T_2分布均会增大;核磁共振T_2谱分布表明,经历180次冻融后,砂岩的孔隙尺寸均会增大,尤其是中、小尺寸孔隙增大明显;在冻融作用下,砂岩的孔隙结构演化,在空间分布上具有分形特征,其分形维数出现逐渐增大的趋势。