Pattullo Bridge Seismic Retrofit & Rehabilitation Project

Project: Pattullo Bridge Seismic Retrofit & Rehabilitation Project
Location: New Westminster/Surrey, British Columbia, Canada
Client: Buckland and Taylor/COWI for TransLink

In early 2014, the Buckland & Taylor/COWI (B&T) team was awarded the contract with TransLink for the preliminary design aspects of the seismic retrofit and rehabilitation of the Pattullo Bridge which spans between New Westminster and Surrey.  M+EG was the geotechnical consultant to B&T for the project.

M+EG's scope of work included the following:

  • Supervision of onshore site investigation work including drilling, sampling and in-situ testing, as well as laboratory testing on recovered samples;
  • Definition of the generalized soil stratigraphy along the bridge alignment, including sub-surface soil conditions and representative geotechnical engineering parameters;
  • Review of the hydrological regime and river bed conditions with consideration of the impact of scour conditions on the foundation design;
  • Seismic design considerations and site-specific seismic response analyses;
  • Assessment of the potential for liquefaction and associated lateral spread;
  • Design of required ground improvement and foundation retrofit schemes to ensure proper performance under the required seismic conditions;
  • Review of aspects related to geotechnical conditions and potential impact on construction.

Project Highlights:

  • Detailed review of historical information during earlier phases of bridge development.
  • Site-specific Cyclic Direct Simple Shear (CycDSS) tests were performed to provide liquefaction resistances of granular soils with high fines contents (silty sand and sandy silt).  The CycDSS results were also used to provide site-specific correlations for liquefaction assessment.
  • Analysis of ground deformations resulting from earthquake loading and the design of remedial measures based on 2D FLAC analyses;
  • Assess different types of ground improvement methods to determine the most effective seismic retrofit scheme for the existing caisson foundations and piled foundation.