DETERMINING THE ORIENTATION OF FRACTURE PLANES IN A WEATHERED CLAY TILL USING CORE SAMPLES

A method has been developed to determine fracture plane orientations i n clay-rich glacial deposits from core samples obtained from inclined borings. In this method, a portion of each core sample is removed to e xpose vertical and horizontal surfaces which are used to map each iden tified fracture plane. An analytical geometry technique is used in con junction with the mapping data to determine the pole to each fracture plane. These fracture pole data can then be presented on a lower hemis phere equal area projection diagram to indicate preferential fracture plane orientations. The utility of the developed method is demonstrate d through a detailed analysis of core samples collected from a 10 m x 10 m site located near Sarnia, Ontario. The data from this investigati on indicated the presence of three sets of fracture planes; however, o nly one of these fracture sets was determined to be statistically sign ificant. The developed method offers an alternative to mapping fractur e plane orientations on exposed surfaces of trench excavations.