Experimental study on quantifying the surface form of artificial tension fractures in granite samples

摘要

The surface form of tension fracture in rock mass influences the seepage of fracture water greatly. How to observe and quantify the fracture surface without destroying the original fracture form (without separating the two surfaces of the fracture) is of great significance to research the water seepage in fracture. In this study, tension fractures were made and developed by filling static expansion agent into drilling holes in granite blocks. Under the condition of keeping the original state of fracture, the sample profiles including the fracture profiles were photographed and measured, and the fracture aperture, opening angle and closing direction along the fracture were measured accordingly. The photos showed that the fracture aperture, opening angle and roughness decreased gradually from the borehole wall (where fractures occur) to the end of the fracture. The measurement results showed that the upper and lower surfaces of the fractures were very similar, just like one surface. Fracture developing pattern was similar to branch extension pattern in structure. The macroscopical trend of the fracture was closely related to the distribution of tensile stress in the specimen before the fracture occurred.