We employed X-ray computed tomography (CT) technology to acquire geometrical characteristics of rock cores in order to characterize multiple joint surfaces that intersect these rock samples extracted at 4.2 km. X-ray CT technology offers the ability to obtain detailed 3D representations of internal and external features based on the density contrast of the forming materials. The characterization was made by estimating the angle of joint intersection in relation to the coring direction and the computation of the joint roughness coefficient (JRC) along each surface. The joints were classified into 2 groups according to their angle of intersection. Almost all surfaces evidence roughness anisotropy, and furthermore the roughness directionality was found to be very similar for group joint"a", where the maximum JRC values gave a mean angle of 161.7 degrees when measured anticlockwise from the horizontal line on the footwall of each joint.
The application of X-ray CT technology to geotechnics started shortly early after its development and introduction to the medical field. Various publications during the 1980's covered areas such as soil mechanics and geotechnics (Mees et al., 2003). In this work, we employed this non-destructive technology to analyze surface characteristics of 16 rock joints that cross core s samples of granite extracted at a depth of 4.2 km from a geothermal project in Pohang, South Korea. The study and characterization of joints is critical for the overall hydraulic and mechanical behavior of the reservoir and rock masses in general. In case of underground structures, rock joints are important because they directly affect the hydromechanical processes such as caprock leakage during geosequestration of fluids or permeability enhancement for engineered geothermal wells (Lewicki et al., 2007).