The depressurization of open pit slopes can be a vital component to achieving design acceptance and improving operational stability. Observed groundwater responses can be influenced by many factors such as pre-mining bulk and near surface enhanced permeabilities, anisotropy, precipitation, and nearby excavation rates. To understand these influences, positioning groundwater monitoring installations near the excavation face are used to provide sufficient resolution to make meaningful observations.
This study investigates the relationship between rock mass, anisotropy, excavation, and blasting influences on the observed groundwater depressurization trends at New Gold's Rainy River Mine located in Ontario, Canada using vibrating wire piezometers (VWPs) installed around the perimeter of the open pit. The study findings are used to verify design stability conditions, and when needed, calibrate pore pressure models.
Trends and correlations are provided for the location specific conditions or monitoring locations at Rainy River Mine. In some examples, the distance from sensor to the pit slope is examined with regards to estimating potential damage zone characteristics and the reasons for the observed response (or lack of). In other examples, packer testing in drillholes inclined behind future pushbacks show little change in tested hydraulic conductivity but unique responses to nearby production blasting.
