Joint spacing distributions from oriented core data

Oriented core drilling data from the East Ertsberg Skarn System (EESS) area of PT Freeport Indonesia were analyzed to help identify the nature of the joint spacing distributions and their impact on block cave fragment size distributions. The normalized frequencies of overall joint spacing and joint spacing within particular joint sets were examined and were modeled using negative exponential and log-normal models. For the joint sets in each of the four different rock types analyzed, the negative exponential distribution was found to provide a good simulation of the actual joint spacing distribution. The parameters of the log-normal distribution (average and standard deviation of joint spacing) needed to be adjusted to provide a good fit to the observed joint spacing. The adjusted log-normal distributions were found to provide a better fit to the observed joint spacing data than the standard exponential distributions.