Influence of joint orientation on key block size distributions

The numerical approach to probabilistic key block analysis is used to evaluate the influence of joint orientation on key block size distribution. A series of tests are conducted by variation of three joint sets. Since joint orientation is recognized by the dispersion of pole vectors (k-factor) so that they are varied. The other joint parameters are kept constant during the test. The relative angle between pole vectors (A) is tested at 90, 60, 30 and 0 degrees from each other. The concentration factor of pole vectors (k-factor) is varied for each different angle. The distribution of key block size is observed from each test. The results show that a unimodal-shaped distribution occurs when k-factor is reduced from 10,000 to 200. When joint plane orientations are random or k-factor is less than 200 the resulting key block size distribution fits a reverse J-shaped Weibull distribution. The fitted shape parameter of Weibull distribution reduces as k-factor is reduced. The angle between pole vectors has less influence on the key block size distribution than does the pole dispersion.