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Over 80 years of experience in structural stabilization and foundation work, including engineering and contractor services related to drilling and grouting, anchor and tieback systems, installation of instrumentation, and cellular concrete and fly ash placement. |
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compaction grouting What is Compaction Grouting? Compaction grouting is the injection of grout into the soil to improve bearing capacity. This is accomplished by using high pressure to expand a bulb of very low slump grout in a controlled manner through an injection pipe. The process has been used successfully for foundation improvement as a precautionary measure under new construction and for remediation of structures that have settled. The Process of Compaction Grouting The process of compaction grouting consists of installation of injection pipes to the bottom of the zone being densified. The pipes are either drilled or driven into place with a sacrificial point. The pipe is withdrawn to open the end of the injection pipe. A specially designed low volume, high pressure pump is used to place the grout. As the grout expands in a homogeneous bulb, the radial force exerted compacts the surrounding soils. A relatively slow injection rate is used to prevent fracturing the soils, allowing water to dissipate and thereby reduce uplift. Injection continues until either refusal pressure is attained or heaving occurs at the surface. Grout placement continues at shallower elevations as the injection pipe is withdrawn in stages. The upward component of force causing heaving at the surface usually limits the degree which soil can be compacted. Precise laser monitoring equipment detects any surface movement. Structures can be re-leveled utilizing compaction grouting. With the use of conventional surveying equipment and laser levels, the surface movement created can be used to raise structures to precise tolerances. Where to Use Compaction Grouting The soils best suited to compaction grouting are fine grained with sufficient permeability to allow excess water to dissipate. The process has also been used successfully in a wide variety of soils and fills. Irregular fills or varying native soils will become more uniform with compaction grouting. An advantage of compaction grouting is the tendency to improve the weakest soils. The effective radius of the grout hole varies with the type of soil being treated. Where large areas are being treated, the primary hole pattern is a diamond or square pattern with holes on 5 to 10 feet (1.5 to 3 meters) centers. Secondary or check holes are placed to the center of the pattern.
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