Compaction Grouting
Pictures
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Contact information
- Dominic Gibbon
- 01937 541118
- geotechnique@keller.co.uk
Process
Compaction grouting is the injection of very stiff, low slump (25-75mm) mortar-type grout under relatively high pressures to displace and compact soils in place.
Soil types
Most effective in cohesionless soils but can also be effective in finer grained soils where disturbance has occurred.
Advantages
- Controlled and accurate placement.
- Predictable degree of improvement.
- High production rates.
- Grouting programme sequenced to site operations.
- Cost-effective; can be implemented when monitored settlement exceeds a pre-determined value.
- Re-compacts soils within vicinity of the problem rather than waiting for settlement to reach adjacent structure foundations.
- All grout pipes can generally be installed outside building.
- No harmful vibrations to nearby structures/utilities.
- Minimum disruption.
Grout types
Normally low slump sand-cement grouts are used with additives.
Method
Grout pipes are installed in a pre-determined design pattern (vertically or angled) to the required depth. Grout is pumped until one or a combination of the following criteria is met:
- Refusal at maximum pressure is achieved.
- A pre-determined maximum grout volume is reached.
- Ground or structure heave is observed.
Product
Homogeneous grout bulb or series of linked bulbs, formed near grout pipe tip as grout pipe is extracted; displacement strengthens and re-compacts adjacent soils.
Quality control
During construction:
- Pressure and grout volume monitoring.
- Monitoring of ground movement.
- Grout tests.
Post-treatment
- Settlement monitoring.
- CPT (Dynamic Cone Testing).
- SPT (Standard Penetration Testing).
