Toronto, Ontario
2004
ECO designed and supervised the execution of an emergency soil grouting program to stabilize the soil below the footing of pier D43 during the construction for the expansion of Terminal 3. The soil below the footing was severely disturbed by an internal erosion process when artesian conditions were encountered during the excavation and construction of the footing of this pier (“boiling footing”). A multiple hole, multiple injection pass grouting program was designed and implemented below the pier’s footing. The particle size analysis of the soils was used to determine the theoretical hydraulic conductivity coefficient. This in turn was compared with the in-situ measured permeability coefficient (via the sleeve pipes) to determine the depth of the disturbance. The grouting program consisted of injecting a microfine cement based suspension grout in the most pervious soil layers followed by the injection of a hydrophobic, semi-rigid, polyurethane based grout in the least pervious soil horizons. All grouting activities were monitored and evaluated in real-time using the CAGES NS system. As a result of the grouting operation, the compressibility coefficient “C” was increased to a multiple of its original value, preventing settlement to the affected column footing.