Oscillation rolling

LOW-IMPACT ROLLOVER HAMM OSCILLATION TECHNOLOGY IS HELPING ASPHALT CONTRACTORS ACROSS THE COUNTRY ACHIEVE MAXIMUM COMPACTION ON SENSITIVE JOBS WHILE USING COMPLEX ASPHALT MIXES.

As one of the great vantage points for Sydney’s New Year fireworks, the Cahill Expressway is situated right in the heart of town. Fittingly, it sits directly over a railway line with enough height to get an unspoiled view of the Sydney Harbour spectacle.

When the road was in need of resurfacing in early 2019, the successful contractor was required to minimise noise and vibrations during works.

The Cahill Expressway runs directly through Circular Quay and is suspended over the main train lines in the CBD, so works were undertaken at night. As a result, noise and vibration needed to be low to minimise any disruptions to the surrounding people and not damage buildings or structures.

Following similar experiences with sensitive compaction projects, Avijohn Contracting was tasked with undertaking the asphalt re-sheeting the expressway.

Michael Kennedy, Operations Manager at Avijohn, knew traditional vibratory rollers would not be able to adequately minimise noise and vibrations on the project, so he turned to another model.

Having previously used HAMM oscillating compaction rollers on the Sydney Harbour Bridge, Avijohn Contracting now owns four oscillating rollers from Wirtgen Australia.

To achieve similar success to that of the company’s works on the Harbour Bridge, Mr. Kennedy decided to use two oscillating rollers on the Cahill Expressway.

Oscillating rollers can minimise noise and vibration impacts, which was a huge enabler for Mr. Kennedy when tendering for bridge works and the expressway.

“When we do work in towards the city around buildings, councils can get

Static Vibration and Oscillation Oscillation

Oscillation and Static

Oscillating rollers have the ability to minimise noise and vibration impacts.

wary about vibration and the potential complaints about vibration, noise and potentially resulting structural damage. A lot of the time it isn’t specified, but we take the oscillation rollers because it’s easier to use them,” Mr. Kennedy says.

Unlike a standard vibratory roller, oscillation drums use two unbalanced shafts that rotate synchronously being driven by a toothed belt. Rather than making the drum move up and down, this produces a backward and forward rotational movement.

The oscillation compaction force acts continuously on the substrate as the drum is in contact with the ground at all times. This enables oscillation rollers to compact dynamically as well as statically with intrinsic weight.

“It’s really hard to achieve proper compaction without vibrating, whereas the oscillating rollers allowed us to safely vibrate and achieve the compaction we needed on the expressway and Harbour Bridge,” Mr. Kennedy says.

Mr. Kennedy says he hasn’t had an issue with a job since he purchased the rollers.

“When operating the machine there is a very noticeable difference from a standard vibrating roller to an oscillation roller. When you are standing next to the running machine you can really feel the difference in vibration,” he says.

“To mitigate the potential for damage around buildings, we take the oscillation rollers.

“We’ve found the oscillation vibration footprint is smaller and it reduces the risk of cracking,” Mr. Kennedy says.

In reducing the impact on surrounding surfaces, oscillation rollers are well suited to confined areas such as around buildings. The reduced transmission of vibration reduces the likelihood of service rupture during compaction.

“Recently we completed a job for a local council with a high-pressure gas main under the road about one metre down. We weren’t allowed to use standard vibrating rollers on top of that to reduce the risk of bursting the pipe.”

Avijohn Contracting used the HD14 and HD17 oscillation rollers for this application and Mr. Kennedy says the council was very happy with the finished results.

Asphaltech Western Australia is another road construction company consistently using the HAMM oscillating rollers from Wirtgen for tough compaction jobs, having purchased a Hamm DV+70 VO-S pivot steer roller in mid 2017.

Peter Rimpas, Asphaltech WA General Manger, says the company does a lot of local government work with oscillation rollers, but one project that stands out is the Barbagallo Raceway resurfacing.

Mr. Rimpas says this was the first racetrack in Australia to be resurfaced with stone mastic asphalt (SMA), traditionally known to be a complex mix to compact.

“A normal vibration drum compacts up and down and if you do this with SMA, there is a chance of the mix flushing” Mr. Rimpas says.

He says because oscillation features the unique compaction technology, there is a significantly reduced risk of SMA flushing.

“We only use oscillation for SMA mixes now because it provides a very strong compaction result.”

Mr. Rimpas also notes the pivot steer DV+ roller has a “crab-steering” function, where both drums pivot and offset the chassis to maximise coverage and increase the working width of the roller.

“With this positioning you end up covering about one-and-a-half times the area that a normal roller would, increasing productivity on the job,” he says.

HAMM oscillation rollers can use two types of dynamic compaction technologies, vibration and oscillation, simultaneously, individually or in static mode.

“We use both vibration and oscillation when we are laying thicker asphalt, around 90-100 millimetres thick. Having both the oscillation drum and vibratory drum is very effective,” Mr. Rimpas says.

HAMM oscillating rollers are also simple to operate. Switching between vibration and oscillation only takes the push of a button.

For road construction, oscillation rollers can compact all base, binder and surface courses.

The drum can be set automatically depending on the rigidity of the material for compaction. This enables quick start-up times for the machine and reduces the risk of error due to incorrect settings.

“For the past two years we have been achieving really good and consistent compaction results, especially with thick layers of dense graded asphalt,” Mr. Rimpas says.