ABSTRACT
The tunnel is predominantly situated in the Queenston Formation of South Ontario which is known to exhibit time-dependent swelling and aggressive ground water conditions and which is expected to present unique challenges in design and construction. In particular shale formations with considerable contents of chloride tend to swell if the concentration of chloride ions contained in the pore fluid of the rock mass is reduced (1). The investigations and resulting conclusions given in this paper are, thus, in particular applicable to these formations.
