Digital superhighways: How Cat MDP technology is taking soil compaction to a new level

During compaction, it’s extremely important that air pockets in the soil are reduced, to ensure the strength of the road foundation strong

For a successful outcome, each phase of the work – soil stabilisation, compaction, grading, material delivery, paving – must proceed with maximum efficiency and always within challenging time constraints.

Understandably, this combination of complexity and time-pressure can lead to less attention being given to some aspects of the project that in fact need more.

A road is the sum of its parts

On a new road project, soil compaction often takes place before other teams arrive on site – and this is one element of the process that tends to gain less scrutiny than it should. After all, errors in this application can result in a lower-quality finish, potentially the need for more maintenance and a reduced lifespan for the surface.

Another consequence of poor soil compaction could be that asphalt rollers need to make more passes, using more fuel, potentially delaying completion and negatively impacting the productivity and possibly profitability of the project, while also leaving the customer less than satisfied.

Skilled and experienced operators have always been key to successful soil compaction

Caterpillar paving specialist Rolf af Klinteberg believes compaction is one phase of a road construction jobsite that rarely gets the attention it should.

“You tend to get entry-level operators on machines,” he says, “and often multiple operators end up working on the same machine and compacting the same area, throughout the day. Overall, there are many opportunities for inconsistencies in compaction results.”

Apart from being unnecessarily time- and energy-consuming, a less than focused approach to soil compaction can lead to failed density tests or stiffness readings. Ultimately, having to go back to the compaction drawing board could have serious implications for the next phases of construction and the overall success of the project.

A scientific approach

The flipside is the potentially sizeable gains to be made from a focused approach to this vital aspect of a road project.

It’s important for road construction crews to have a good understanding of soil types, to ensure successful compaction

af Klinteberg believes it’s critical to the success of a road project that senior crew members have some understanding of soil science – or, at the very least, soil types – to the extent that they can select the correct machines and methods to optimally compact the road’s base layer.

Given that the two main classifications of soil are granular and cohesive, one might think the process of squeezing pockets of air out of it to increase density ahead of construction is relatively simple. Not quite…

“All soil behaves differently,” says af Klinteberg, “so it’s extremely important to select the correct type and size of machine for a specific job. Using the wrong machine on a specific application could mean that, not only is an area over or under compacted, but the chance of damaging the material also increases.”

Granular soil, for example, is easily molded, but is also more prone to crumbling. Generally speaking, the best type of compaction for this soil is vibratory compaction.

Rolf af Klinteberg, a product application specialist with Cat Paving

According to af Klinteberg, “This is because a mass in motion has velocity, which is converted to energy at the instant of impact. This impact creates a pressure wave that goes into the ground from the surface.

“Due to its vibratory system and the high static linear load over the drum, it creates greater compaction force than a machine that relies on gravitational force only [a non-vibratory system].”

A vibratory compactor can be used for all soil types, usually with a smooth drum for non-cohesive or granular soil, and a padfoot drum (featuring serrated protrusions) on semi-cohesive or cohesive soil.

Letting tech take the strain

Digital technology is being brought to bear on many aspects of road construction, including soil compaction.

Caterpillar has recently attempted to redress the balance with a number of digital products, allowing contractors to test the water with entry-level tech, before scaling up.

The Machine Drive Power (MDP) system is a simple but effective piece of operator assistance that works on the principle of rolling resistance.

The energy-based measurement system, unique to Caterpillar, matches compaction to rolling resistance to give an indication of soil stiffness. A mapping system option can also help operators visualise the work as it progresses.

af Klinteberg offers a neat analogy to describe the basic operation of MDP. “Imagine pushing a loaded wheelbarrow over a concrete sidewalk,” he says, “and then through some soft garden soil.

“Minimal effort is required to push the wheelbarrow on the concrete, but a lot of effort is needed to push it through the garden soil. This is because the concrete is stiffer and has higher load bearing strength, supporting the wheel firmly, rather than sagging under its weight.

Cat Paving’s latest technology for soil compaction is set to boost productivity and reduce error

“Machine Drive Power measures the amount of power required for the soil compactor to propel over the soil, providing an indication of the load bearing strength.”

In this way, with real-time compaction values visible on the machine display, MDP can help operators achieve uniform compaction in fewer passes, reducing fuel consumption as well as overall machine wear and tear.

Additionally, values are captured and documented by a mapping system that can help ensure optimal compaction on future projects.

The MDP system is a clever and extremely straightforward in-cab upgrade on traditional compaction methods, which basically involve counting the number of passes and using external measuring methods, such as accelerometers.

Operator as process monitor

For contractors looking to utilize more advanced technology, Caterpillar offers Cat Command for Compaction, an operator-assisted, semi-autonomous system that automates the compaction process, based on operator inputs.

Good soil compaction is literally the basis for every good road project

“Command controls the speed, direction, steering and vibration system of the soil compactor, to promote consistency in compaction,” says af Klinteberg.

This system is based on the number of passes required to complete the compaction, rather than a stiffness value.

In practice, it’s as simple as telling the machine where to compact and how many passes to make; from that point, it’s semi-autonomous.

An operator uses the machine itself to create the boundary within which the machine will compact – basically hitting a record button on the monitor, before operating the machine along the boundary lines.

The only other necessary instructions are the number of passes, the ground speed and the required overlap. Once the operator commences the program, the Command system will control the speed, direction, steering and vibration of the machine.

According to af Klinteberg, “Caterpillar has continued to invest in integrating the critical layers of automation to help solve customer challenges and make them more successful.”

Right now, though, Cat technology has obvious benefits for contractors who may be rotating operators on a single compaction area, or who have a number of less experienced operators on the team. Command for Compaction, for example, is designed to help maintain uniform compaction, even when the soil requires multiple passes.

Ultimately, the level of technology and expertise brought to bear on the soil compaction phase of a road project is a personal choice. It is worth noting, however, that it will have a bearing on the end result and therefore on the prospects of more and more successful work in the future – in much the same way as the paving process.

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This article was produced by KHL Content Studio, in collaboration with experts from Caterpillar Inc.

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All images courtesy Caterpillar Inc.