Construction sites worldwide have witnessed a transformation in soil compaction methods with the emergence of High Energy Impact Compaction (HEIC). This innovative technique employs specialized Impact Rollers (IR) – equipped with triangular, rectangular, or polygonal wheels – that are towed by tractors to deliver powerful ground vibration force. Unlike traditional compaction methods that laboriously work with thin 200mm lifts, HEIC achieves deeper penetration while saving both time and money, making it a game-changing solution for modern construction projects.
How Do They Work?
The high-impact energy compaction method can be considered a lighter version of the dynamic compaction method. It works by creating a vibration of the underlying soil by the impact of the lifting and falling of the roller drum weight from a certain height.
Courtesy: M.I. PINARD, S. OOKEDITSE
The falling converts the potential energy to kinetic energy. The kinetic energy induces vibration in the soil and the soil particles respond by rearranging themselves to a more dense position.
The flat contact area with the ground also increases the depth of influence which results in more depth of compaction.
Suitability of HEIC compaction
The selection of the type of Impact roller depends on the soil type moisture regime and depth
of treatment needed. The effect of compacting soils with HEIC treatment varies with soil type, in-situ moisture content, and Specific Energy Input.
The Specific Energy Input of the Impact rollers is selected by optimizing by choosing the appropriate impact drum weight, drum shape, drum compaction coverage and drop height to suit the given in-situ material types and site conditions
Courtesy: Helics group
The factors to consider in rightly choosing HEIC for a project include:-
1. Soil Types:
HEIC is most effective in granular soils with low fine content.
2. Depth of Influence:
HEIC can typically compact soils to depths of 1.5-3m.
3. Site Conditions:
HEIC is particularly suitable for large areas and thick layers of fill.
4. Limitations:
The effectiveness of HEIC decreases in soils with higher silt or clay content.
5. Moisture Content:
HEIC can work effectively over a wider range of moisture contents. particularly dry of OMC
| Soil/Site Condition | Suitability |
| Granular soils with low fines content (<15%) | Highly suitable |
| Soils with 13-30% fines | Suitable |
| Soils with <13% fines | Very suitable |
| Soils with <2% fines | Highly suitable |
| Loose, compressible granular soils | Suitable |
| Soils with high silt or clay content | Less suitable |
| Large areas requiring compaction | Highly suitable |
| Sites requiring deep compaction (1.5-3m) | Suitable |
| Sites with thick fill layers | Suitable |
| Sites with varying moisture contents | Suitable |
| Reclaimed lands and landfills | Suitable |
HEIC roller types and their specifications
The specific energy inputs of HEIC rollers of the brands on the market range from 10 to 28 kJ/m. Typically the weight and drop height of the drum modules range from 8 to 12 tonne and 150 to 230 mm, respectively.
The amount of the specific energy input depends on the size, shape, and drop height of the HEIC drums, Thus affecting the depth of influence and the magnitude of increase of the in-situ soil strength
For the high energy impact that can densify layers of thickness 2-3m, the rollers are required to be pulled at relatively high speeds (typically about 6 to 8 mph)
Research conducted on the subject indicates that the HEIC ground improvement process can improve weak soils to depths of 4-5m below the compacting surface, across a spectrum of weak natural sands, weak reclaimed sand deposits and un-compacted/un-controlled variable clay fills.
Types of HEIC machines
There are several brands of impact compactors to suit various project needs. Mainly they are categorised by the shape of the drums.
1. 3-Sided Impact Compactor: Ideal for smaller projects or areas with limited space.
2. 4-Sided Impact Compactor: Offers a balance between compaction area and maneuverability.
3. 5-Sided Impact Compactor: Provides the largest compaction area, suitable for extensive projects.
Courtesy: Helics Group,
| Brand | Roller Type | Drum Size (m) | Drum Weight (kg) | Drop Weight (kJ) | Specific Energy Input (kJ/m³) |
| Gram Conveyor | 3-sided | 1.5 | 12 | 25 | 16.67 |
| Insitutek | 3-sided | 1.5 | 12 | 25 | 16.67 |
| Broons | 4-sided | 2.0 | 15 | 30 | 15.00 |
| Sinoway | 3-sided | 1.6 | 12 | 25 | 15.63 |
| Sinoway | 5-sided | 2.0 | 16 | 32 | 16.00 |
| Cofra | 4-sided | 2.0 | 15 | 30 | 15.00 |
| Menard | 5-sided | 2.5 | 18 | 35 | 14.00 |
Working Formula for Field Engineers
The assessment of the project’s suitability needs the consultation of a geotechnical engineer to make an informed decision based on soil tests, site conditions, and project requirements.”
For field engineers looking to implement HEIC, here’s a practical approach:
The first step in applying the HEIC process is conducting a full review of available geotechnical data as a baseline of project information. The baseline data of the geotechnical status of the project serves to assess the suitability of the various module configurations for the given soil type and site conditions.
The information gathered before the application of the treatments is used to compare the impact after the application of the method.
The development of HEIC technology in recent years has improved the understanding of the soil response during its application. The relationship between the depth of influence and the improvement in in-situ soil strength has become more predictable.
The steps of geotechnical assessment for HEIC include:-
1. Soil Assessment: Evaluation of the soil type and site conditions before compaction.
2. Equipment Selection: Choose the appropriate impact compactor based on project requirements (3, 4, or 5-sided).
3. Pass Planning: Determine the number of passes needed based on soil type and desired compaction level.
4. Monitoring: Utilize real-time monitoring systems to track compaction progress and ensure quality assurance.
Soils assessment, monitoring, and verification in HEIC application
The effectiveness of HEIC can vary significantly based on site-specific conditions. As noted in the “Ground Improvement” chapter of the ICE Manual of Geotechnical Engineering (2012):
“The success of any ground improvement technique depends on a thorough understanding of the site conditions, including soil stratigraphy, groundwater conditions, and the presence of any obstructions or sensitive structures nearby.”
To address this, it’s crucial to:
Conduct a comprehensive site investigation before the HEIC application.
Establish correlations between different test methods for the specific site conditions.
For example:
- Correlate DCP results with CPT data for the specific soil types at the site.
- Relate ICM readings to actual soil density and strength measurements.
- Compare plate load test results with DCP and CPT data to understand the relationship between penetration resistance and bearing capacity.
There are three steps of project application steps:-
1. Pre-Compaction Assessment
- Determine soil type and moisture content
- Establish target density requirements
- Select appropriate HEIC equipment based on project specifications
2. During Compaction
Real-Time Monitoring
Most modern HEIC equipment incorporates advanced intelligence monitoring systems called Intelligent Compaction Measurement (ICM). Such modern systems have sensors on their drum axles that can help correlate deceleration with the change of stiffness of the ground and can monitor the effectiveness of the compaction in real time. This enables continuous Impact Response Monitoring during operation.
Modern HEIC rollers are equipped with the following capabilities that can result in high efficiency and quality of compaction.
- Ground stiffness measurement: Sensors attached to the drum axle measure soil stiffness at each location.
- GPS mapping: Provides a visual representation of compacted areas and pass counts.
- On-board displays: Show real-time compaction data to operators.
Pass Count Tracking
HEIC typically requires multiple passes in overlapping patterns:- Use GPS-equipped rollers to track the number of passes and ensure uniform coverage of the treatment area. The passes that are applied in the operation consist of:_
- Primary rolling in a clockwise direction
- Secondary/intermediate rolling in an anticlockwise direction
The number of passes and offsets between tracks depends on project specifications and the specific impact roller used.
3. Post-Compaction Verification
After compaction, various tests are performed to verify the achieved density:
In-Situ Density Tests
- Cone Penetration Tests (CPT): Commonly used to assess compaction effectiveness.
- Nuclear Density Gauge or Sand Cone Test: For measuring in-place density.
Stiffness and Bearing Capacity Tests
- Plate Load Test: Measures bearing capacity and settlement characteristics.
- Dynamic Cone Penetrometer (DCP): Assesses the strength of compacted layers.
Data Analysis and Reporting
- Compare pre- and post-compaction test results to evaluate improvement.
- Analyze depth of influence, typically ranging from 1.5m to 3m depending on soil type.
- Generate compaction maps and reports using brand-specific software.
- The potential of geophysical methods for assessing larger areas.
Application cases of High Energy Impact Compaction (HEIC) or Impact Rolling (IR)
1. Industrial and Commercial Development:
“Bunnings Stores at Epping and Scoresby.”
“Three-hectare Direct Factory Outlet at Brisbane Airport (fill over weak alluvium)”
“Two-hectare supermarket and specialty shop development at Leopold”
2. Residential Development:
“One-hectare residential subdivision at Wantirna”
“Two-hectare residential subdivision at Merrylands”
“4.25-hectare residential development at Varsity Lakes (fill over weak clay and loose sand, ground improvement included soil wicks and preloading)”
3. Landfill and Brownfield Sites:
“Ceres Environmental Park, Brunswick. New 1000m2 reception center on high energy impact compacted landfill that is up to 20m deep in an old bluestone quarry.”
“Police station at Croydon (Vic) on an old service station site with areas of non-engineered fill up to 3m deep adjacent to natural soil”
“Taren Point. Five-hectare site developed as a retirement village on up to 3.5m of refuse. High energy impact compaction was for pavements only.”
4. Industrial and Warehouse Developments:
“5.5-hectare factory/warehouse development at Chullora”
“Four-hectare industrial subdivision at Riverwood”
“Three-hectare factory/warehouse development at Brisbane Airport (fill over weak alluvium)”
5. Infrastructure Projects:
“4.4-hectare container terminal at Altona (pavement only)”
“0.5 hectare switchyard at Cairns”
6. International Projects:
“Two-hectare site in Pudong (Shanghai) with 2-3m of uncontrolled fill including refuse over 20m of soft to firm ‘Pudong mud’ developed as a factory and two-story office for Parker Hanifan.”
7. Coastal and Resort Developments:
“1.9-hectare site at Nelly Bay, Magnetic Island, on 2-7m of sand/clayey sand fill developed with twelve 3-4 level buildings on high-level strip footings for the Blue-on-Blue resort.”
“1.75-hectare site at Palm Cove to be developed on interbedded loose to dense sands and soft to stiff clays as four level plus basement hotel and apartments on high-level slab footings.”
8. Office Developments:
“Toyota Motor Corporation Head Office. Port Melbourne. Four-storey office on high-level strip and pad footings, on 2m of sand fill over loose sand with weak ‘Coode Island Silt’ at about 6m.”
“Four-hectare office development in Port Melbourne on 2m of sand fill over loose sand.”
These application cases demonstrate the versatility of HEIC/IR in various construction scenarios, particularly in sites with challenging soil conditions, fill materials, or where deep compaction is required.
Results of HEIC application
The application of HEIC results in Soil densification due to vibration and particle re‐organization are increase in Friction angle, Stiffness, and Bearing capacity. Ultimately it can also mitigate Liquefaction and Limit settlement when load is applied.
Higher operating speeds of 10 – 13 kph, and increased depth of influence result in increased productivity – up to 10 times greater volume than the conventional method
The results of some research done provide a clear indication of the depth of influence of the high-energy impact compaction process and the significant increases in soil strength for a natural “marine” sand and other granular materials, a reclaimed sand deposit, in-situ mixed fill, landfills, and low-strength natural soils and for a variable clay fill.
Benefits of HEIC:
– Deeper compaction compared to traditional methods
– Faster project completion times
– Cost-effective for large-scale projects deep without the need for costly and time-consuming displacement foundation systems, pre-loading or excavations
– Ability to compact thick layers of soil
– Real-time monitoring for quality assurance
– increased productivity – up to 10 times greater volume than conventional methods.”
Limitation of HEIC:
– May require specialized training for operators
– Initial equipment cost can be higher than traditional compactors
– Not suitable for all soil types or project scales
– The high-impact forces disturb (i.e., loosen) the top 0.25 to 1.5 ft of the surface so the top layer needs additional compaction with conventional rollers.
-The vibrations caused by the impact rollers and their effect on nearby structures (e.g., underground utilities/pipelines or nearby building structures) are important to consider with this technology.
Sources:
1.https://www.academia.edu/77138623/High_Energy_Impact_Compaction_HEIC_Utilization_for_Shallow_Depths_of_Fill
2.https://www.researchgate.net/publication/276090007_Compaction_of_Subgrade_by_High-Energy_Impact_Rollers_on_an_Airport_Runway
3. https://www.landpac.co.uk
4.https://journalofcivilengg.com/journal/journalofcivilenggarticle/High-Energy-Impact-Compaction-(HEIC)-Utilization-for-Shallow-Depths-of-Fill-Densification/102/
6.https://journalofcivilengg.com/journal/journalofcivilenggarticle/High-Energy-Impact-Compaction-(HEIC)-Utilization-for-Shallow-Depths-of-Fill-Densification/102/
7. https://heic.co.za/heic/
8.https://www.menard-group.com/soil-expert-portfolio/high-energy-impact-compaction-heic/
9.https://www.academia.edu/77138623/High_Energy_Impact_Compaction_HEIC_Utilization_for_Shallow_Depths_of_Fill