High Energy Impact Compaction (HEIC) for large-area ground improvement
High Energy Impact Compaction (HEIC), also known as impact rolling or rolling dynamic compaction, compacts large areas using a non-circular roller (typically three-, four- or five-sided) towed at speed. As the roller turns, its mass rises and falls onto the ground, delivering high-energy impacts that densify near-surface soils and fills more deeply than conventional vibratory rolling.
Suitable ground conditions and applications
Can be considered where…
- Large-area granular fills and earthworks platforms.
- In-situ densification of near-surface loose sands and collapsible soils.
- Roads, airfields, industrial yards and laydown areas.
- Proof-rolling to locate soft or weak zones before construction.
Limitations
- Treatment depth is shallower than Dynamic Compaction or Rapid Impact Compaction.
- Needs large, open areas for runs at operating speed.
- Saturated fine-grained soils respond poorly.
- The surface is left uneven and needs final trimming and smooth-drum rolling.
Suitability is confirmed from the site investigation and the performance requirement.
How it works
The roller is towed by a high-powered tractor unit. Its flat faces and corners make the centre of mass rise and fall as it rotates, so each face strikes the ground as an impact rather than a static or vibratory load.
The roller passes over the area in a planned pattern. The number of passes is set by trial: the surface settlement after each set of passes shows how the ground is responding, and compaction continues until the response levels off or the criteria are met.
Design inputs
- Site investigation: soil profile, moisture content, groundwater level.
- Fill material and thickness, if treating fill.
- Performance criteria: target density, stiffness or settlement.
- Required depth of improvement.
- Available area and run lengths; distance to structures and services.
Trial and calibration
- Baseline tests (e.g. density tests, CPT or plate load tests) on a trial pad.
- Level survey after set numbers of passes to build the settlement-passes curve.
- Post-treatment tests compared with the baseline and the criteria.
- Number of passes and pattern agreed for production.
Execution controls
- Pass count and pattern for each area, tracked by GPS where available.
- Towing speed within the agreed range.
- Level surveys at agreed pass intervals.
- Moisture condition of fill material.
- 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
Target density, stiffness or settlement criteria agreed with the consultant.
What was done
Pass counts, speed and level change recorded for each area.
What was proven
Field density tests, plate load tests or CPT against the criteria.
Deliverables
- Method statement and risk assessment
- Treatment area plans
- Trial report with agreed passes
- Pass records and coverage maps
- Level surveys
- Verification test reports
Common questions
How deep does HEIC improve the ground?
HEIC works on the near-surface layers. The depth reached depends on the soil, its moisture and the roller energy, and is confirmed on site by a trial with testing before and after.
What is the difference between HEIC and a normal roller?
A conventional roller applies static weight or vibration through a round drum. An impact roller has a non-circular drum that strikes the ground as it turns, so its effect reaches deeper and thicker layers can be compacted.
What size of site suits HEIC?
Large, open areas where the roller can travel at operating speed in long runs. Small or confined sites are usually better suited to other methods.
Discuss whether High Energy Impact Compaction (HEIC) fits your ground conditions.
Share the site location, the investigation report and the performance requirement.