Improvement of the concept of the blockiness level of rock masses

Abstract

The concept of blockiness level, which enables the measurement of the jointing degree of rock mass in three dimensions, is limited due to some significant shortcomings. In this study, to tackle the limitations, the guidelines for the applications of the concept were formulated according to the calculation basis of blockiness level. Then, a more reasonable computational method of the blockiness level was proposed, the ratings for the blockiness levels and corresponding jointing degrees of rock mass were modified, and the improved concept of the blockiness level was validated and supported through the artificial data. Finally, the improved concept was applied to two real cases, i.e., the Wudongde Hydropower Project (China) and the underground powerhouse of the Three Gorges Project (China). Different discontinuity network models, which were generated by deterministic discontinuities and following the Discrete Fracture Network approach, respectively, were presented in the two case studies, and the results show that the blockiness levels of the two adits (i.e., PD49-1 and PD 4) in Wudongde Hydropower Project are 12.847% and 10.168%, respectively, both belonging to the relatively integrated category, and the blockiness level of the underground powerhouse of the Three Gorges Project is 3.6‰, falling into the integrated category. The improved concept of the blockiness level was found to be acceptable and practicable.