Coupled HM effects in a crystalline rock mass due to glaciation: indicative results from groundwater flow regimes and stresses from an FEM study

This paper highlights certain aspects of glacial impact on groundwater flow and rock mechanics, of particular interest in future scenarios for the geological disposal of nuclear waste. The investigation took the form of a generic exercise based on conditions at the underground research facility in Whiteshell, Canada. The site scale model domain boundaries were set up based on a number of major deformation zones. The surface boundary conditions comprised a transient ice sheet load and related hydraulic heads, generated by meltwater. It has thus been possible to compare glacial impact in relation to present-day climatological conditions. The main issues in the investigation were to evaluate the groundwater flow regime and the pre-requisites for underground jacking as well as shearing according to the prescribed geoscientific properties of a benchmark protocol. Special attention has been devoted to a solution to the hydromechanical (HM) problem (1) with or without process coupling, (2) with or without a transient approach, and (3) considering a two- or three-dimensional mode. The study underlines the need for transient analyses in 3D of these coupled phenomena.