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Compaction Grouting is the injection of grout into soil to achieve controlled displacement and densification of the surrounding soil mass.
Used For:

Densifying and strengthening foundation soils

Controlled lifting of structures

Mitigating settlement due to tunneling

Preventing soil liquefaction

Providing additional soil-strengthening benefits

Background of Technique
Applications
Foundation & Soil Densification
Controlled Lifting
Mitigation of Tunnel Settlements
Prevention of Soil Liquefaction
Materials & Equipment
Summary

Background of Technique>

Compaction Grouting is a specialized technique for in-situ densification of compactable soft or loose soils. A stiff grout is extruded into a soil mass to form an expanding bulb. Maintaining a controllable bulb of grout is the essences of this technique, as illustrated in Figure 1 .

Any soil capable of being mechanically compacted can be densified by compaction grouting. The extent and the intensity of soil densification depends on the injection point configurations, the depth of the injections, the grout mix, and the amount of grout injected. Compaction grouting is effective in most man-made fill, organic soil, sand, silt, peat, and most clays. The improvement of soil strength can be demonstrated by the Cone Penetration Testing Method before and after compaction, as shown in Figure 2 .

Figure 1

Applications

Compaction grouting is versatile: it lifts, levels, stabilizes, supports, fills and densifies soil for new construction and existing structures, and it also reduces machinery vibration. The Pressure Grout Company has completed hundreds of successful projects involving compaction grouting for:

Building Sites–Site improvement for structural support and prevention of soil liquefaction
Building & Structures–Settlement mitigation, foundation stabilization, controlled lifting
Machinery Pads–Controlled lifting and leveling, stabilization, vibration reduction
Tunnelling–Surface settlement prevention, heading stabilization
Drilled Piers–Lifting to grade without excavation, restoration of deformed pipes
Pipelines–Lifting to grade without excavation, restoration of deformed pipes
Tiebacks–Anchor development

Figure 2

Hundreds of jobs have established that compaction grouting is an effective and economic method of compacting soils.

Foundation & Soil Densification & Strengthening

Compaction grouting can provide an answer to the problem of differential settlement of structures. The versatility of the technique makes it the method of first choice for soil densification in areas where access to the site with heavy equipment is difficult or where noise is a problem. Grout injection points can be angled to reach areas under a foundation that otherwise could not be reached, as shown in Figure 3.

Figure 3

Controlled Lifting

Compaction grouting can be used effectively for the controlled lifting of foundations, slabs, and other structures. Lifting takes place when the pressure at the bulb exceeds the weight of overburden, structures, and the shear strength of the soil cone above it. At that point, the soil shears, and the grout pressure lifts the soil and the structure built upon it, as shown in Figure 4.

Figure 4

By the careful use of this technique, entire structures can be lifted and leveled to precise specifications. Unlike other lifting or supporting techniques, compaction grouting supports structures and appurtenances on sound soil foundations.

Mitigation of Tunnel Settlements

Tunelling generally produces ground movements, which are manifested in the form of surface settlements or the loosening of adjacent soil and rock. Compaction grouting can be used for the prevention of surface settlement, for heading stabilization, and for remedial work in adjacent soil.

Prevention of Soil Liquefaction

Compaction grouting can be effective in reducing or eliminating the liquefaction potential in earthquake-prone areas. For unimproved sites or for existing structures, the technique can be successfully employed to avoid soil liquefaction. For deep liquefiable soil layers, for inaccessible sites, or for sites where noise can not be tolerated, compaction grouting is the primary choice for achieving soil densification without vibration or impact.

Materials & Equipment

Compaction grouting is accomplished by using a lean, thick grout mix of portland cement and silty sand. Natural sands with a range of 25 to 30% silts usually are used. The water content of the grout is adjusted to maintain a slump (ASTM C-143) of 1 to 1.5 in., with a maximum of 2 in.

The Pressure Grout Company has designed and built much of the equipment it uses on compaction grouting assignments. This equipment, capable of achieving grouting pressures of up to 2000 psi, can be operated at distances several hundred feet from the injection site. The operation of Pressure Grout Company at a job site is shown in Figure 5 .

Figure 5

The Pressure Grout Company Summary

The Pressure Grout Company has extensive experience in all types of pressure grouting for site development, new construction, and the stabilization of existing structures, ranging from giant dams and highrise buildings to individual homes and buildings of all types. We work closely with owners, engineering firms, contractors, and public agencies through the United States. We:

Build, operate and maintain our own equipment
Have one of the few research and development laboratories for grout materials and mixes
Have a staff that includes engineers with extensive knowledge and experience in soils engineering
re licensed contractors and members of the Associated General Contractors and
Have broad, in-depth grouting experience that extends over a period of more than 45 years