Joint set intensity estimation: comparison between investigation modes

Recent mathematical calculations allow us to define set fracture intensity (I), i.e., the amount of rock mass affected by fracture sets, independently of the investigation mode. This parameter, characteristic of each rock mass, is of much interest to describe the mechanical response of the rock mass to external influences. The aim of this work is to apply these mathematical equations on one site using measurements of three distinct fracture sets: (1) on a plane surface, (2) along a scanline, and (3) using borehole imaging, in order to evaluate and explain variability in collected data. Even if the three types of measurements give differences on absolute intensity values, they still define similar trends, i.e., the order of the fracturing impact of joint sets is the same from the three measurement methods, irrespective of the fact that obtained values are quite different from one survey method to another. We discuss the possible origins of these biases.