Abstract Manager

Caisson Design in Georgian Bay Shale at QEW/Credit River Bridge:  A Case Study with Bi-Directional Static Load Testing

Ministry of Transportation Ontario:  Tony J. Sangiuliano, Minkyung Kwak

WSP Golder: Joe Carvalho, Lisa Coyne

Rock-socketed drilled shaft (caisson) foundations for MTO projects have traditionally involved relatively long sockets relying on a significant proportion of sidewall resistance, which may not take full advantage of the base resistance.  A recent MTO design-build project for twinning of the QEW/Credit River bridge in Mississauga incorporated a shorter, more efficient rock socket design in the weak to medium strong Georgian Bay shale.  We will discuss MTO’s focus on innovation in alternate project delivery, the basis for the geotechnical design of the rock-socketed caissons, and the results of an axial bi-directional static load test, also called an Osterberg cell or “O-cell” test, that was completed as requested by MTO to validate the ultimate sidewall and base geotechnical resistances of the rock socket on a test shaft.  The caisson base cleaning procedures were verified using a Shaft Quantitative Inspection Device (SQUID), and the concrete integrity in the test shaft was assessed using crosshole sonic logging (CSL) and thermal integrity profiling (TIP).  These results expand the knowledge base for caisson foundation design in the Georgian Bay shale formation, and demonstrate the effectiveness of SQUID, SCL and TIP in quality control during construction.