Experimental study of the visible seepage characteristics and aperture measurement of rock fractures

• Published in: Arabian journal of geosciences 2021-09, Vol.14 (17), Article 1795
• Main Authors: Li, Zheng, Liu, Jie, Zhang, Yan, Guo, Jianxiang, Li, Zhao, Tang, Hongyu, Shi, Qian
• Format: Article
• Language: English
• Subjects: Additives; Apertures; Digital imaging; Earth and Environmental Science; Earth science; Earth Sciences; Flow velocity; Fracture surfaces; Image processing; Measurement; Mechanical properties; Model matching; Modulus of elasticity; Original Paper; Rocks; Roughness; Seepage; Technology; Vectors; Velocity; Visibility; Water flow
• ISSN: 1866-7511; 1866-7538
• DOI: 10.1007/s12517-021-08154-4

Aiming at solving the problems of physical model visibility and repeatability in natural rough rock fracture seepage tests, the method of determining the additive ratio of rock-like materials by using natural rock elastic modulus as the target variable was put forward and a transparent resin fracture model that matched perfectly with the original fracture surface was fabricated. A visual seepage test device that could accurately obtain the seepage area, flow path, and velocity vectors from the mesoscopic perspective was developed. After processing the test video at the millisecond level, the flow velocity was calculated by using the method of layer superposition to draw the flow velocity vector graph. The results showed that the water flow in a filled fracture had a significant nonlinear spatiotemporal evolution phenomenon. At the same time, the mapping results with the roughness contour map were combined to show that the dominant seepage channels are mainly distributed in the region with JRC values of 0~4.0. The water in the fracture accelerates and gathers along the main flow path at fracture dip angles of 60–90°, which proves that the low roughness area is the dominant seepage channel. A new idea of measuring fracture aperture was put up, which was to measure the fracture apertures of any point on the flow path by using bubbles through digital image processing technology. It was found that the average aperture could be obtained precisely by calculating the area of the actual seepage area. The above research can provide a new method for the study of fracture seepage characteristics and the measurement technology of fracture apertures in the laboratory.