Braced Sheet Pile Shoring Wall in Sensitive Clay

This case history describes the design and performance of a temporary braced sheet pile shoring wall constructed within the median between heavily-trafficked lanes of the Trans Canada Highway in Langley near Vancouver, British Columbia, Canada. The excavation extended to 9.7 m depth below the existing road grade into soft, high plasticity, sensitive glaciomarine clay. Glaciomarine clay is locally notorious for excavation and embankment stability and foundation settlement problems. The shored excavation was required to provide an access pit to allow the installation of a 3 m diameter steel pipe culvert by Horizontal Pile Driving (HPD). The braced sheet pile wall was designed using the Terzaghi Apparent Earth Pressure distribution and conventional limit equilibrium analysis methods. The excavation was undertaken in stages as the bracing was installed and ground deformation was monitored using slope inclinometers and by survey of surface targets. The case history describes the performance of the excavation and compares predicted to monitored displacements. A particular issue related to face stability due to clay squeezing and running sand during bulkhead sheet pile removal required to commence HPD for culvert installation. The bulkhead face was stabilized by grouting with a water reactive polyurethane grout prior to sheet pile removal