The Role and Versatility of Dynapac Padfoot Compactors

[MikePhua]

Dynapac’s Legacy in Soil Compaction
Founded in Sweden in 1934, Dynapac has long been a leader in compaction and paving equipment. The company introduced its first vibratory roller in the 1950s and quickly became known for innovation in soil and asphalt compaction. Today, Dynapac operates globally, with manufacturing facilities in Europe, Asia, and North America, and its padfoot compactors are widely used in infrastructure, mining, and land development projects.
Padfoot rollers—also known as sheepsfoot compactors—are designed for cohesive soils like clay and silt. Unlike smooth drum rollers that rely on surface pressure, padfoot drums penetrate and knead the soil, increasing density from the inside out. Dynapac’s padfoot models combine high centrifugal force, vibration, and static weight to achieve deep compaction in fewer passes.
Understanding Padfoot Drum Design
The padfoot drum is a cylindrical steel shell covered with protruding rectangular or tapered pads. These pads concentrate force into small contact areas, allowing them to break down soil structure and eliminate air pockets. The drum may be equipped with:

• Fixed pads: Welded directly to the drum for maximum durability
  
• Bolt-on pads: Replaceable for different soil types or wear conditions
  
• Scraper bars: Prevent soil buildup between pads
  
• Vibration system: Enhances compaction by shaking soil particles into tighter arrangement
  

Dynapac padfoot rollers typically range from 5 to 20 tons in operating weight, with drum widths between 1.5 and 2.2 meters. Models like the CA250PD and CA3500PD are popular in highway construction and dam building, where deep, uniform compaction is critical.
Applications and Performance Benefits
Padfoot compactors excel in environments where moisture content is high and soil cohesion resists penetration. Common applications include:

• Road subgrade preparation
  
• Embankment construction
  
• Landfill cell development
  
• Pipeline trench backfill
  
• Foundation pad stabilization
  

In one highway project in Queensland, Australia, a Dynapac CA3500PD was used to compact clay embankments for a bridge approach. The machine achieved 95% modified Proctor density in just three passes, outperforming a smooth drum roller that required double the effort.
Operating Techniques and Best Practices
To maximize padfoot performance, operators should consider:

• Moisture control: Ideal compaction occurs when soil moisture is near optimum. Too dry and the soil crumbles; too wet and it pumps under pressure.
  
• Pass count: Most cohesive soils require 4–6 passes for full compaction. Excessive passes can lead to over-compaction and surface cracking.
  
• Overlap strategy: Maintain 15–20% overlap between passes to ensure uniform coverage.
  
• Speed regulation: Operate at 3–5 km/h for effective pad penetration and vibration transfer.
  
• Pad wear monitoring: Inspect pads regularly for rounding or cracking, which reduces effectiveness.
  

Dynapac’s compaction meters and onboard diagnostics help operators monitor soil stiffness and adjust technique in real time. Some models offer GPS integration for pass mapping and density tracking.
Maintenance and Longevity
Padfoot rollers are subject to intense mechanical stress and abrasive conditions. Key maintenance areas include:

• Drum bearings and seals: Grease regularly and inspect for leaks
  
• Hydraulic system: Monitor pressure and fluid cleanliness
  
• Vibration exciter: Check mounting bolts and balance weights
  
• Pad condition: Replace worn or damaged pads to maintain compaction quality
  
• Engine and cooling system: Clean radiators and air filters to prevent overheating
  

A contractor in Texas reported that his Dynapac CA250PD ran over 4,000 hours before needing pad replacement. Regular cleaning and lubrication extended drum life and reduced downtime.
Conversion Options and Drum Flexibility
Some Dynapac padfoot models offer conversion kits to switch between padfoot and smooth drum configurations. This allows contractors to use the same machine for cohesive and granular soils. Conversion involves:

• Removing bolt-on pads
  
• Installing smooth drum shell or overlay
  
• Adjusting scraper bars and vibration settings
  

This flexibility is especially useful in mixed-soil projects or rental fleets where versatility is key.
Stories from the Field
In a dam construction project in Kenya, a Dynapac padfoot roller was used to compact clay core material. The operator noted that the machine’s ability to knead and bond the soil layers reduced seepage risk and improved structural integrity. Engineers credited the compactor’s performance with helping the project meet international standards for soil density and compaction uniformity.
In another case, a landfill operator in Ontario used a padfoot roller to compact daily cover material. The pads broke up frozen clay and prevented surface crusting, improving gas venting and leachate control.
Conclusion
Dynapac padfoot compactors are more than just heavy rollers—they’re precision tools for shaping and stabilizing the earth. Their ability to penetrate, knead, and densify cohesive soils makes them indispensable in modern construction. With proper technique, maintenance, and soil awareness, these machines deliver consistent results that stand the test of time and terrain. Whether building highways, dams, or industrial pads, the padfoot roller remains a cornerstone of deep compaction excellence.