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CAT® Machine Drive Power technology leads compaction results

Sound soil compaction is vital to the integrity of the construction process. New technology from Caterpillar delivers precision, increased productivity, fuel saving and reduced operator fatigue. Caterpillar compaction product specialist Darren Hodge digs into the latest technology.

Soil compaction is a vital process in construction as it is the basis of support of nearly all structural entities – building foundations, roadways, walkways and earth retaining structures.

The Australian construction industry has generally enjoyed high adoption rates when it comes to new technology in earthmoving products – particularly those delivering precise finish design surface levels, elevations, and shape as well as providing increased productivity, lowering fuel burn and reducing operator fatigue.

Cat® Soil Compactors are now benefiting from similar advancements with a range of technical features to assist the operator in determining when they have reached final compaction density.

Put simply, compaction is critical. It is a process that cannot be compromised on any project. Reaching the compaction specification to achieve surface load-bearing strength is critical to maintaining a stable surface structure into the future.

Typically, meeting compaction density on-the-job has been based on operator intuition because there is generally a lack of real-time feedback on the actual state of compaction.

Operators generally rely on their experience to judge when compaction is achieved and will often complete more passes than necessary before testing is carried out to confirm density has been met.

This means unnecessary passes and incorrect compaction processes, which may affect a contractor’s ability to complete the job on time, ensure quality control and ensure efficient fuel consumption.

Fortunately, there is now a smarter way.

An exclusive new Cat feature available on our B Series vibratory soil compactors, Machine Drive Power (MDP) is an innovative soil compaction measurement technology to help operators determine when the load bearing strength of the soil has met the desired specification.

Knowing this result in real-time adds significant productivity, allowing the operator to move on to the next area maintaining timeliness.

The new MDP option measures rolling resistance to determine soil stiffness and has a wider scope of application compared to conventional accelerometer-based measurement systems used.

Conventional systems commonly use a formula that is calculated by measuring the drum rebound with an accelerometer to provide an indication of soil stiffness.

However, the Cat MDP alternative is an ‘energy based measurement’ that determines rolling resistance and the amount of energy necessary to overcome it.

This measurement is then correlated to soil stiffness.

alternative is an ‘energy based measurement’ that determines rolling resistance and the amount of energy necessary to overcome it. This measurement is then correlated to soil stiffness.

The MDP advantage means it can be used in all soil types with both smooth drum and pad foot compactors, and with the vibratory system on or off. In particular MDP technology provides advantages over traditional accelerometer based systems that have limitations particularly in cohesive materials.

Caterpillar recently carried out a demonstration using a Cat CS56B Soil Compactor fitted with MDP with a contractor to show how this new technology could help improve its business and reveal the benefits of a ‘smart’ compactor. The demonstration area was in a land area where the majority of soil materials needed to be hauled in from nearby quarries (due to poor existing soil structure).

Caterpillar started the demonstration by establishing a target compaction value using MDP. This was to be achieved by completing a number of passes until the MDP value read out was within ± 2 units of variation indicating compaction had been reached.

In this case the target value recorded from MDP value was achieved with four compaction and one proof roll passes.

To confirm the outcome of compaction using MDP value a sand penetrometer test was performed to confirm the density. The MDP value correlated on average to 10 blows via the penetrometer. This exceeded the target number of blows on site of eight. This process and the resultant confidence in the MDP system allowed the contractor to reduce the pass counts from 12 to only four, plus one for the proof roll.

For the purposes of the test site, this is the equivalent to a 50 per cent reduction in the area covered, which correlates to obvious savings in time and fuel consumption for that scenario in question.

Further compaction demonstrations on the same job using MDP also discovered a potential problem or soft area.

In this instance the material was a mix of the Class B sand and the natural material found onsite. After establishing a target value of 125, the MDP technology identified an area with a value of 115 – below the target.

Another penetrometer test was completed resulting in nine blows, which was only just above the required eight blow target.

Through further investigation it was found that this area had inconsistent material content compared to the rest of the area – it contained more natural soils than hauled-in class B sand.

The demonstration provided the contractor with a terrific illustration of the productivity and fuel efficiency gains potentially available using the technology, but also helped it understand how MDP could provide another layer of quality control in its operation.

To further establish the benefits of using MDP to help the operator determine when the load bearing strength of the soil being compacted had met specification, we conducted an exaggerated simulation of soft spots in an area and then attempted compaction.

A tyre was buried in the job site pass area and we challenged the operator to find it in the area he was attempting to compact. The spot, which had not met the MDP target value, was clearly identified in the satellite mapping display on board the machine.

It was an interesting exercise and can be viewed on YouTube, see ‘The Buried Tyre Challenge’:

  • Traditional Compaction Meter Value (CMV) via LCD display
  • New MDP option with standard LCD Display
  • New MDP option with Satellite Mapping on a colour display monitor


MDP allows contractors to start out with a basic system and add more capability as needs grow.

The basic measurement system includes MDP measurement technology. Mapping capability can then be added, with two levels of accuracy currently available.

The Cat B Series Soil Compactor range of products have a number of other features all designed to benefit productivity, provide ease of operation and target lower ownership and operating costs.

In particular, the propulsion system, which has dedicated dual hydraulic flow for both the drum and rear axle drive, delivers excellent traction on both steep grades and deep lifts on all Cat rollers.

From a serviceability and maintenance standpoint, the revolutionary Cat pod-style proprietary eccentric weight design and vibratory system comes with an industry leading 3 year/3000 hours recommended service interval and maintenance free articulation hitch bearings.

With such a wide range of features and innovative class leading technology, Cat rollers are designed to do the job efficiently, precisely and productively.

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