Physical Modeling of Foundations for Northumberland Strait Crossing

Abstract

The 13-km-long Northumberland Strait Crossing will become the longest continuous marine span bridge in Canada. The marine and navigational spans of the bridge will be supported by 44 precast concrete piers founded on bedrock using ring-shaped footings in a maximum water depth of 35 to 40 m. Bedrock stratigraphy ranges from massive strong sandstone to a variable sequence of thinly bedded weak mudstones and siltstones. Foundation conditions vary significantly from pier to pier and in several cases can vary through the vertical and lateral extent of a particular foundation. In addition to the complex foundation conditions, the large horizontal environmental loadings on each pier must be considered in the geotechnical analyses. Reduced-scale physical model tests of selected marine piers on a centrifuge investigated potential mechanisms of failure and examined how these mechanisms varied with loading and foundation conditions. The results of the experimental program were used in conjunction with analytical results to enhance the fundamental understanding of the geotechnical aspects of foundation design and have led to an improved design methodology.