68th Canadian Geotechnical Conference and 7th Canadian Permafrost Conference

INFLUENCE OF ROCKMASS PROPERTY VARIATIONS ON PRE-MINING STRESSES: A CASE STUDY

Session: Rock Mechanics and Engineering Geology II / Mécanique des roches et ingénierie géologique II

Shahé Shnorhokian, McGill University (Canada)
Hani Mitri, McGill University (Canada)
Lindsay Moreau-Verlaan, Vale Canada Ltd. (Canada)

Variations in rockmass properties are commonly encountered in underground mines. When undertaking numerical modeling, the selection of different rockmass input properties can result in a wide range of results. In this paper, a simplified mine-wide model of a deep Canadian metal mine is constructed in FLAC3D to study the influence of variations in rockmass properties on pre-mining stresses at two drift locations 1500 m below ground surface. It is calibrated using boundary tractions based on an in-situ stress measurement point. Laboratory results and borehole data are analyzed to determine the minimum, average, most likely, and maximum rockmass strength levels. It is observed that pre-mining stresses plotted for the drift locations follow regular patterns that depend on the rockmass properties of the formation in which the readings are taken, as well as other influential units. The methodology uses a range of vertical stress values to narrow down a large number of variations in rockmass properties into a smaller set that is realistically possible in the field. It is shown that the possible range of stress levels at locations of interest can be assessed, and key formations that influence the readings identified.