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Compaction Grouting (Low Mobility Displacement Grouting)

Compaction Grouting is also commonly known by the generic names Low Mobility Displacement Grouting or simply Low Mobility Grouting. The technique involves the delivery of low mobility grout via open ended tubes (drill casings) drilled or driven to pre-determined depths. The grout, typically containing cement, sand, fly ash and water, is placed in stages, from bottom of the hole upwards, with pressure-based and volume-based refusal criteria. Between consecutive stages, the casing is retracted upwards until the delivery tube is completely removed.

Stage dimensions and volume refusal criteria are determined on a hole by hole basis, after drilling, but prior to grouting. Grout injection rate and pressure are dictated by the soils' ability to redistribute the increased stresses and dissipate pore water pressures and are often modified as the grouting program progresses.

The low mobility grout displaces the existing soil creating grout bulbs in situ. Benefits of this process include densification and consolidation of the soil and creation of vertical grout columns.

As the technique involves displacement, it is particularly effective in disturbed soils. Most of Geo-Foundations' past compaction grouting jobs have come about as a result of our clients needing to repair disturbed soil for reasons such as over-excavation during tunneling, long-term migration of fine particles through broken sewer pipes, water main rupture, or past poor compaction of placed fill soils.

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