A review of discontinuities in Georgian Bay Formation Shale observed during Greater Toronto Area tunnelling projects

Abstract

A further understanding of the discontinuities, including key joint set orientations, that characterize Georgian Bay Formation Shale (GBFS) is desired to aid in the design of underground construction and tunnelling projects in the Greater Toronto Area (GTA). Numerous ground investigations (GI) and tunnel construction face mapping projects, completed for local tunnelling projects, have amassed a large collection of data. The results of televiewer data and face mapping can be analyzed together to characterize the discontinuity trends including bedding planes, distinct joint sets, fault, and shear orientations on stereonets. The interpretive element to identifying emerging sets on stereonets will be guided by a review of the existing GBFS literature, the far field structural setting, and considering the geological ground model. The results can also provide useful information to assess groundwater inflows and conduct wedge analysis, lining design, and more.