ABSTRACT
The engineering properties of the Ordovician rocks are extremely variable due to the range of rock types and variation of weathering, jointing and cleavage found in the rocks. The Ordovician rocks typically consist of alternating beds of graded sandstones, siltstones, shales and slates. Bed thicknesses can range from a few centimetres to several metres. The Ordovician rocks at the Rosslynne damsite comprise bedded sandstones, siltstones, shales and slates, with sandstones and siltstones being dominant. The Ordovician rocks show a wide range of strength depending on the rock type, weathering state and degree of cementing. The laboratory test data available for the Ordovician rocks shows a wide variation of engineering properties, dependent mainly on the rock type and degree of weathering. The presence of often alternating beds of variable thickness and the presence of secondary cementing, cleavage and fissuring in some rock sequences further adds to the variation of the engineering properties for the Ordovician rocks.
