Rock Quality Charts Based on Cumulative Intact Lengths

The rock quality charts (RQC), based on the cumulative intact lengths in evaluating fracture spacing along scanline surveys or drill cores, provide a convenient and rapid means of quantifying a fundamental rock mass property. These charts are obtained by plotting successive cumulative intact lengths that are greater than 0.1 m (0.3 ft or 4 in.) against the fracture locations along the scanline. The segments that are smaller than this threshold value are considered as zero lengths in cumulative summation. The points obtained in this way are connected by straight line segments, hence a non-decreasing pattern emerges which shows the actual intact length variation along the scanline length. For instance, horizontal segments indicate the existence of weak zones. The cumulative intact length pattern supplements the rock quality designation (RQD) by providing additional and detailed information at any point along the scanline.