Investigation of Permeability Characteristics of Rock Under Confining Pressure-Fracture Coupling Conditions

This paper presents applications of 3D printing to investigate the failure mechanism of a fractured rock sample under the coupling effect of stress-seepage. 3D printing technology was used to prepare fracture inserts covering ten levels of surface roughness (JRC = 1-10), four different fracture thicknesses (1 mm, 2 mm, 4 mm and 5 mm) and four types of geometric structures (2 equal, three equal, four equal and five equal). Permeability tests were carried out to study the factors influencing the test scale on the permeability characteristics of the rock mass. The results show that permeability decreases with increasing fracture roughness. This behaviour, as expected, is less pronounced in samples with larger fracture apertures. The results show that, in order of increasing importance, the permeability of the fractured rock samples depends on confining pressure, fracture aperture, network geometry and fracture surface roughness. A dimensionless parametric area ratio of fracture connection beta is proposed when looking at the problem from a quantitative perspective and based on the physical mechanism of seepage in fractured channels; using this approach, it is possible to reduce the dimensional influence of the experimental scale. Highlights center dot Experimental methods were used to study the crucial factors affecting fracture development and permeability combined with 3D printing technology. center dot The key influencing factors on permeability are confining pressure > fracture width > fracture geometry > fracture surface roughness. center dot A dimensionless parameter area ratio of fracture connection is proposed for the first time to reduce the scale effect. center dot This paper presents a method to calculate the permeability of fractured rocks on a larger scale in the field by experimental and theoretical means.