Determining the orientation of fracture planes in a weathered clay till using core samples

A method has been developed to determine fracture plane orientations in clay-rich glacial deposits from core samples obtained from inclined borings. In this method, a portion of each core sample is removed to expose vertical and horizontal surfaces which are used to map each identified fracture plane. An analytical geometry technique is used in conjunction with the mapping data to determine the pole to each fracture plane. These fracture pole data can then be presented on a lower hemisphere equal area projection diagram to indicate preferential fracture plane orientations. The utility of the developed method is demonstrated through a detailed analysis of core samples collected from a 10 m × 10 m site located near Sarnia, Ontario. The data from this investigation indicated the presence of three sets of fracture planes; however, only one of these fracture sets was determined to be statistically significant. The developed method offers an alternative to mapping fracture plane orientations on exposed surfaces of trench excavations.