Rapid Impact Compaction (RIC) for ground improvement
Rapid Impact Compaction (RIC) densifies granular soils and fills using a hydraulically driven hammer that repeatedly strikes a steel foot resting on the ground. Because the foot stays in contact with the surface, energy is applied in a controlled way, which suits RIC to shallow-to-moderate depth treatment.
Suitable ground conditions and applications
Can be considered where…
- Loose granular soils and fills at shallow-to-moderate depth.
- Sites where more control and less vibration than Dynamic Compaction are needed.
- Building platforms, tank foundations, roads and yards.
- Treatment of collapsible soils before loading.
Limitations
- Treatment depth is less than Dynamic Compaction.
- Saturated fine-grained soils (clays and silts) respond poorly.
- Vibration is lower than DC but still needs monitoring near assets.
- The excavator-mounted rig needs a stable working platform.
Suitability is confirmed from the site investigation and the performance requirement.
How it works
The hammer is lifted hydraulically and dropped onto a steel foot that stays on the ground. Each blow drives the foot down, densifying the soil beneath and around it.
Points are treated on a grid, often in primary and secondary passes. Treatment at each point stops when the agreed criterion is met, typically a minimum penetration per blow (the set), or a maximum number of blows. The rig records blows and penetration for every point.
Design inputs
- Site investigation: soil profile, CPT/SPT results, fines content, groundwater level.
- Performance criteria: bearing pressure, settlement, target test values.
- Required depth of improvement.
- Grid spacing and passes.
- Stopping criteria: set per blow and maximum blows.
- Distance to structures and services.
Trial and calibration
- Baseline CPT before treatment.
- Treatment with trial parameters, logging penetration per blow at each point.
- Post-treatment CPT and plate load tests compared with the baseline.
- Grid spacing and stopping criteria agreed for production.
Execution controls
- Setting out of every point against the approved grid.
- Blow count and cumulative penetration per point from the rig data logger.
- Stopping criteria checked at each point.
- Backfilling and levelling of depressions between passes.
- Daily production records.
Verification and acceptance
Design intent, production control and acceptance verification are kept separate, so it is always clear what was required, what was done and what was proven.
What is required
Performance criteria and target test values agreed with the consultant.
What was done
Data-logged blows and penetration for each point.
What was proven
Post-treatment CPT, plate load tests or zone load tests against the criteria.
Deliverables
- Method statement and risk assessment
- Treatment grid drawings
- Trial report with agreed criteria
- Rig data logs for every point
- Level surveys
- Verification test reports
Common questions
Which soils are suitable for Rapid Impact Compaction?
Loose granular soils and fills. Saturated clays and silts respond poorly, because the impact raises pore-water pressure instead of densifying the soil.
Should I use RIC or Dynamic Compaction?
RIC applies lower energy with closer control, which suits shallow-to-moderate treatment depths and work closer to existing assets. Dynamic Compaction reaches deeper but needs more clear space around the work.
How is RIC controlled during production?
The rig records the number of blows and the foot penetration at every point. Treatment at a point stops when the agreed penetration per blow or the maximum number of blows is reached.
Discuss whether Rapid Impact Compaction (RIC) fits your ground conditions.
Share the site location, the investigation report and the performance requirement.