Riggs was retained by Higgs Construction Ltd. to provide civil and structural engineering services to complete construction of a new pumping station in Strathroy, Ontario.
The project required shoring which involved braced excavation and dewatering prior to construction. The high water table at the site and clay lenses in the soil layer were considered in the static equilibrium analysis of the steel sheet pile wall. These conditions generated additional pressure on the wall.
The solution involved consideration of the available steel sheet pile material that the contractor had in supply and the physical restrictions at the site. Riggs was able to eliminate the internal cross bracing and the use of deep sections for steel wales in order to permit free and unrestricted access to the pit for the construction work.
Riggs was hired to develop an underwater lateral load testing program for testing the integrity of reinforced concrete caisson piles installed adjacent to a ferry dock in Leamington, Ontario.
As part of rehabilitation works to increase the depth in front of a dock, 914 mm diameter concrete caissons, spaced 2.5 m apart along the length of the dock, were drilled into bedrock in order to underpin the existing sheet pile wall and provide a deeper dredge grade for the local ferry. During the installation of caissons the contractor encountered ground conditions previously undetected.
The top of the caissons were underneath 6-8 m of water, thereby limiting the ability in using conventional pile integrity testing equipment.
In order to verify the integrity of the caissons, an underwater lateral load test was designed to monitor load-deformation behaviour to a sub millimeter scale using divers and an underwater Linear Variable Displacement Transducer (LVDT). The measured load-deformation curves were compared to theoretical pile movements computed via the p-y method using soil properties estimated from conventional and self boring pressure meter results.
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