Geotechnical Seismic Assessment of A Pile Supported Wharf and Implications For Future Upgrades

The existing South Jetty wharf structures at the Esquimalt Graving Dock were evaluated with respect to current seismic performance requirements and a possible future upgrade design was developed. These facilities, located in one of the highest seismic hazard regions in Western Canada, were originally constructed in the 1940s. The ground conditions at site consist of sloping, interbedded fills overlying the Victoria Clay, which overlies bedrock. The liquefaction potential of these materials, as well as potential liquefaction induced displacements, are the key issues affecting the seismic performance of the existing jetty, and any future upgrades. Site investigation and advanced cyclic simple shear testing were carried out to assess the liquefaction potential of fills and strain softening potential of Victoria Clay. Liquefaction assessment showed that the sloping interbedded fills would liquefy under the design earthquake, however the Victoria Clay would not trigger liquefaction. Deformation analyses showed that the fills would undergo very large displacements, and the existing structure would not meet the current seismic performance criteria. The foundations for the new structures were designed to withstand the effects of liquefaction induced displacements. This paper presents a summary of the seismic assessment and the preliminary design of the redevelopment of the jetty.

Cross, R.A. and A. Port. 2015. “Geotechnical Seismic Assessment of a Pile Supported Wharf and Implications for Future Upgrades,” Proceedings of the 11th Canadian Conference on Earthquake Engineering (11CCEE), Canadian Association of Earthquake Engineering, July 22-24, Victoria, BC.