Numerical Investigations of Blockiness of Fractured Rocks Based on Fracture Spacing and Disc Diameter

Abstract

Some numerical models treat masses of rock as assemblages of isolated blocks, whereas others treat them as continuous material. It needs to be determined at what level a rock is cut into assemblages of discrete blocks by fractures. This paper used a parameter B to measure the degree to which rocks form an assemblage of blocks; B is a dimensionless number in the range 0.0<B<1.0 and is defined as the ratio of the aggregated volume of individual blocks in the investigated domain to the total volume of the rock mass in the investigated domain. The quantitative description scheme for fracture spacing and persistence suggested by the International Society for Rock Mechanics (ISRM) was used to construct different types of fractured rocks to conduct investigations into blockiness. Seventy-seven different types of fracture networks were studied. The fractures investigated covered all the fracture spacing and persistence ratings suggested by the ISRM. Based on the blockiness of the 77 samples, an analytical function was established to describe the relationship between the blockiness and the fracture spacing (S) and fracture disc diameter (D). The resulting function is an S-shaped curve.