| dc.description.abstract | Low-permeability rocks are often used as the main geological barrier in natural gas storage, carbon dioxide storage and nuclear waste disposal. Low-permeability rock is dense in structure, low in pore volume, and permeability mainly dominated by its fractures. However, the overly large mass and the complex discontinuity make it unfavorable in the in-situ test which measures the relationship between flow pattern of fluid in fractured rock mass and deformation characteristics of fracture. In recent years, 3D printing technology has gradually matured. Using digital model as the foundation, 3D rock model is constructed by stacking and accumulating through photosensitive resin and gypsum powder. The technology has various advantages such as easy modification, requires no molds and fast forming and has been applied in rock mechanics fields for academic exploration. In order to investigate the permeability behavior of fractured network rock mass under different confining pressures and the closure characteristics of fractured forces, this study used the fracture parameters (fracture center position, aperture, fracture radius, and orientation) to generate a fracture network; the fractured rock mass cylindrical specimen was printed using photocuring 3D printing technology, and the permeability and pore volume measurement were performed using a high confining pressure pore volume/permeability instrument. At the same time, the theoretical calculation method is used to calculate the hydraulic average aperture under the same fracture network permeability. The hydraulic average aperture is then compared with mechanical average aperture, which is found via pore volume measurement. The permeability values measured by the four specimens ranged from 1.73×10-12 m2 to 2.73×10-12 m2 (confining pressure is between 0.3 MPa and 4 MPa), while the pore volume ranged from 715.92 mm3 to 1331.35 mm3. (confining pressure is between 1MPa and 4MPa). The calculated hydraulic average aperture is between 37.25μm and 43.75μm (confining pressure is between 0.3MPa and 4MPa), which is less sensitive to stress; the calculated mechanical average aperture is between 86.73μm and 161.29μm (confining pressure is between 1MPa and 4MPa), and its sensitivity to stress is high. Through the fitting of two different aperture closure models of hyperbolic and semi-logarithmic curves, it is found that the correlation coefficient between the two models of mechanical average aperture closure is between 0.91 and 0.99, which can well describe the relationship between the mechanical average aperture closure and the effective stress. The correlation coefficient for the fitting of the hydraulic average aperture closure is between 0.18 and 0.86, because the hydraulic average aperture is less sensitive to effective stress. The ratio between mechanical average aperture and hydraulic average aperture is between 2.13 and 4.21. | en_US |