Constellation, le dépôt institutionnel de l'Université du Québec à Chicoutimi

Résumé

The most commonly used method for assessing the hydraulic erodibility of rock is the Annandale's method. This method is based on a correlation between the force of flowing water and the capacity of rock resistance. This capacity is evaluated using the Kirsten's index which was initially developed to evaluate the excavatability of earth materials. This index is determined according to certain geomechanical factors, such as the compressive strength of intact rock, the rock block size, the discontinuities shear strength and the relative block structure. This last characteristic represents the required effort to erode the rock and, it can be quantified considering the rock block's shape and orientation relative to the direction of flow. To determine the relative rock structure in the field, the dip and dip direction of closer spaced joint set, as well as the ratio of joints spacing are required. It is found that the Kirsten's concept can be applied only when the direction of flow is perpendicular to the strike of closer spaced joint set. Our proposed communication focuses on the adjustments introduced to Kirsten's initial concept concerning the relative block structure parameter. Thus, two equations are proposed to evaluate the impact of rock block's shape and orientation when the direction of flow is not perpendicular to the strike of closer spaced joint set.