The size and distribution of pores in rocks are closely related to their physical and mechanical properties. It is important to study the structure and distribution of pore size inside the rock to assess the risk of damage to a given rock volume. These characteristics were studied under different pressures, pore diameters, and pore throat size distribution laws using a UTM5540 electronic universal testing machine, magnetic resonance imaging scanning, and low field nuclear magnetic resonance spectroscopy with cyclic loading on yellow sandstone. We found the following. (1) Under 0–10 MPa load, the peaks of the sandstone spectrum move left as load increases, and the porosity of the sandstone decreases. The peak area of the middle relaxation spectrum increases as pressure increases from 10 to 20 MPa, and a peak for the long relaxation time spectrum appears. (2) Under 0–10 MPa load, the spectral peak associated with a large pore moves left and decreases in area as pressure increases. Under 10–20 MPa load, the large-pore spectral peak moves right and increases in area as pressure increases. (3) Under the applied 0–10 MPa load, the porosity of water-saturated sandstone gradually decreases, and the sandstone NMR images darken with increasing load. The porosity of saturated sandstone gradually increases under 10–20 MPa pressure, and its NMR image brightens. (4) The number of small pore throats increases with increasing load, but the number of large- and medium-sized pore throats decreases. From 0 to 15 MPa, crack (>1 micron) abundance decreases, and fractures are generated by compaction under a 20 MPa load. The pore interconnectivity is enhanced, as are the number and size of pores in the sandstone. With continuing increasing pressure, the numbers of pores and penetration of cracks increase, which damages the sandstone.

中文翻译：

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循环荷载作用下砂岩孔隙大小的变化特征

岩石中孔隙的大小和分布与其物理和机械性能密切相关。重要的是研究岩石内部的孔径结构和分布，以评估破坏给定岩石体积的风险。使用UTM5540电子万能试验机，磁共振成像扫描和在黄色砂岩上循环加载的低场核磁共振波谱，在不同的压力，孔径和孔喉尺寸分布规律下研究了这些特性。我们发现了以下内容。（1）在0-10 MPa的载荷下，砂岩的峰随着载荷的增加，光谱向左移动，砂岩的孔隙率降低。中间弛豫谱的峰面积随压力从10 MPa增加到20 MPa而增加，并且出现长弛豫时间谱的峰。（2）在0-10 MPa的载荷下，与大孔相关的光谱峰向左移动，并随着压力的增加而减小。在10–20 MPa的载荷下，大孔谱峰向右移动并随着压力的增加而增大。（3）在施加的0-10 MPa载荷下，水饱和砂岩的孔隙度逐渐降低，并且随着载荷的增加，砂岩NMR图像变暗。在10–20 MPa压力下，饱和砂岩的孔隙度逐渐增加，其NMR图像变亮。（4）小孔喉的数量随负荷的增加而增加，但大中型孔喉的数量减少了。从0到15 MPa，裂纹（> 1微米）的丰度降低，在20 MPa的载荷下压制会产生裂缝。孔隙连通性增强，砂岩中孔隙的数量和大小也得到增强。随着压力的不断增加，孔的数量和裂缝的渗透增加，从而损坏了砂岩。