Results of Trial Grouting at Ontario Power Generation's Sir Adam Beck Pump Generating Station Reservoir, Niagara Falls-Paper

Paper

Pdf Summary

Ontario Power Generation conducted trial grouting before installing a 1.2 km grout curtain beneath the Sir Adam Beck Pump Generating Station reservoir dyke. The curtain was intended to reduce seepage and the risk of foundation piping associated with sinkholes and depressions that had developed around the dyke.<br /><br />Two trial panels, each containing primary and secondary grout holes, tested a two-stage method: grout the overburden–bedrock contact through Multiple Pass Sleeve Port pipes (MPSPs), then grout the bedrock. Inflatable barrier bags attached to the MPSPs were intended to isolate the contact zone from the overlying materials. The panels were excavated after grouting to inspect the pipes and surrounding ground.<br /><br />Excavation showed that the barrier bags inflated adequately and that grout filled the annular space above them. However, six of eighteen holes had voids immediately below the bags. Overburden had also entered or filled the rock sockets in several holes, potentially obstructing contact grouting. The overburden–bedrock interface and exposed bedrock were generally more competent than anticipated, with little evidence that contact treatment was needed.<br /><br />Based on these findings, the production design eliminated grouting of the overburden and contact zone, focusing treatment on bedrock to at least 3 m into the Rochester Shale. MPSP installation was modified so barrier bags were partly embedded in bedrock. After low grout takes in early production holes, sleeve-port injection below the bags was also eliminated in favour of open-hole bedrock grouting. The trial indicated that tertiary holes would likely be needed beyond secondary holes to achieve curtain closure.<br /><br />The authors conclude that the trials were important for identifying risks, refining the installation and grouting methods, and informing production requirements. Close collaboration among the owner, engineers, and contractor supported the changes.

Keywords

Ontario Power Generation

trial grouting

grout curtain

Sir Adam Beck Pump Generating Station

seepage control

foundation piping

sinkholes

Multiple Pass Sleeve Port pipes

bedrock grouting

Rochester Shale