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Micropiles

Micropiles are a deep foundation system consisting of small diameter (305 mm or smaller), drilled, replacement elements consisting of high strength steel and cement grout, that transfer axial loading to the earth via grout-to-ground sidewall friction. Micropiles are typically used in situations where above-ground or below-ground conditions render the use of conventional deep foundations impractical, too difficult, or too risky to the health of neighbouring structures or services.

Micropiles are classified by numerous sub-types, each determined by the combination of widely varying drilling and grouting installation processes. Drilling methods include double-head duplex, rotary percussion, continuous grout flush, and rotary with polymer flush just to name a few. Grouting methods include straight tremie injection, dynamic grouting, pressure grouting during casing retraction, and tremie-injection with post-grouting.

Geo-Foundations has designed and constructed more than 130 micropile projects across Canada. The vast majority of these projects included at least one static compression load test to 200% of micropile design loading. At the Pembroke Courthouse, in boulder-rich till with no embedment in rock, load testing was successfully completed to 2600 kN applied compression and 1400 kN applied tension. At the Art Gallery of Ontario, with rock sockets constructed 18 metres below surface in shale bedrock, static compressive load testing was successfully completed to 7100 kN on a single 273 mm diameter micropile, and to 8050 kN on a pair of 194 mm diameter micropiles.

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