Settlement Performance of the Burlington Bay Skyway

The Burlington Bay Skyway is founded on a deep baymouth bar which is believed to be about 10 000 years old and to be normally loaded with respect to present ground level. Beneath the northern half of the bar there is a considerable depth of clay, which is also believed to be normally loaded under the weight of the bar. Bedrock occurs directly beneath the southern half.The skyway is symmetrical about Burlington channel, which is approximately centrally located along the length of the bar. Foundations include 74 piers and the abutments. Two main piers are carried on steel H-piles acting in friction, while 20 other piers on the north side are founded on short timber piles. All other piers, and the abutments, are founded on spread footings. The superstructure is of steel construction incorporating plate girder and rolled steel beam spans with continuity in units of three and four spans, respectively. Computations carried out during design indicated that differential settlements could exceed tolerable limits for continuous spans. Provision for shimming was therefore made, and settlement observations taken to provide the necessary control.The results of the settlement readings are presented primarily as a case history, along with a number of unusual features in the foundation subsoil arising out of its origin as a deep bar deposit.