不同储藏气压下含气土细观结构表征与重构研究

含气土的储藏气压与细观结构表征是研究浅层气地质灾害的关键因素。利用工业CT扫描测试系统，采用立式旋转扫描，微焦点X射线光源的位置固定，样品沿XY平面方向匀速旋转1周，设定旋转步长为0.3°/s，对反应釜内含气样品注气加压至2 MPa、4 MPa、6 MPa，充分考虑样品成像最佳分辨率、最佳探测范围等因素的影响。结果表明，CT扫描获得的切片图像与重构图像具有良好的实验效果；加压注气到2 MPa时，小气泡灰度值增加；加压到6 MPa时气体整体灰度值增加明显；增压过程中气泡数量随着气泡半径增加而减少；加压注气过程会导致固−液−气三相物质局部变化，表现为孔隙气、孔隙水的体积变化幅度整体大于土骨架，微观局部位置会有较大的升高或降低。当不同位置的气体含量上升且占据主导地位时，会驱动着孔隙水的减少与土骨架的移动。

Characterization and reconstruction of meso-structure of gas-bearing soils at different storage pressures

The storage pressure and reconstruction of the mesostructure of gas-bearing sediments are key factors in the study of shallow gas geohazards. Using an industrial CT scanning test system, vertical rotational (SR) scanning is used, with the position of the microfocus X-ray source fixed and the sample rotated at a constant speed of 360° along the XY plane, with a set rotation step of 0.3° per second, the gas-bearing samples in the reactor are pressurized to 2 MPa, 4 MPa, and 6 MPa, taking into account the best resolution of the sample imaging, the best detection range and other. The results show that the slices and reconstructed images obtained from the CT scan have good experimental results; the greyscale values of small bubbles increase when pressurized to 2 MPa; the overall greyscale values of gas increase significantly when pressurized to 6 MPa; the number of bubbles decrease with increasing bubble radius during the pressurization process; the pressurization process lead to local changes in the solid-liquid-gas phase, which show that the volume of pore gas and pore water changes more than that of the soil skeleton. The overall change is greater than that of the soil skeleton, and the microscopic local location will have a greater rise or decrease. When the gas content at different locations rises and dominates, it will drive the reduction of pore water and the movement of the soil skeleton.