The 3D Advantage Helps Hawaiian Contractor Meet Spec, Reduce Waste Jas. W. Glover, Ltd. (Glover), a locally owned and operated Hawaiian general contracting company specializing in concrete and asphalt paving, found similar advantages when tasked with the re-construction of Runway 8R-26L, also known as the Reef Runway at the Honolulu International Airport on the island of Oahu. The FAA and the Hawai’i Department of Transportation (HDOT) required that each section of the runway take no longer than 15 days to complete, with stiff penalties written into the contract for missing deadlines. To increase milling and paving production at the Reef Runway, Glover added a 3D paving control system on an additional Roadtec RX-900 mill and Cat AP1055D paver. The system included four more total stations and two rovers for topos, layout and checking grade. The firm ran two 12.5’ wide 3D mills and two 25’ wide 3D pavers to keep up with production. The ability to control the milling elevation, and placing material to elevation with the pavers while maintaining slope and smoothness without stringline or wires was key to the project success. Each machine was controlled by a total station, and Glover crews used additional total stations to leapfrog every 1,000 feet without having to stop the machine. The company built the 3D models in Trimble Business Center software. The 3D design is then transferred to the machine and displayed to the operator to show areas that are on, above, or below ideal grade comparing the actual drum position and slope with the digital design. The system automatically guides the milling drum to cut the ideal depth and slope without stringlines or manual adjustments. Not only did the paving control system on the milling machines provide a smoother base for paving, that smarter milling means they have to remove less waste material and mill off the minimum depth only. According to the company executives it would have been nearly impossible to mill everything to the new profile without using 3D technology because of the existing variable slopes of the runway. They say the technology saved crews huge amounts of time and manpower in terms of layout, topos and establishing where the grades should be. The owner was also pleased with the smoothness of the runway surface, noting that there were zero grinds on the finished product and elevation was within specification. In fact, Glover met the half-inch grade tolerance, quarter inch up or down for the entire length of the runway. With 3D milling and paving machine control from Trimble, the company was able to lay 5,000 tons of asphalt to grade and slope per night, in a 12-hour shift compared to 2,000 or 2,500 tons per shift, on other jobs.
control the screed to pave with variable depth and slope based on a 3D design. It can take out high and low areas on the first layer as the screed follows the design for slope and thickness. The system automatically lays the right amount of asphalt for improved accuracy and increased productivity. By avoiding excess asphalt placement, the system increases road smoothness, which can also lead to potential bonus pay on projects that offer such incentives. It also means not having to spend time setting out While 2D paving solutions are well adopted in the industry, 3D can be a difficult investment decision for contractors, despite the proven ROI. It’s one reason why technology developers are introducing subscrip- tion-based models to help contractors transition. Subscription-based services such as Trimble Platform as a Service (TPaaS), available in North America, give contractors the ability to purchase certain hardware and software solutions for a set monthly price and get full technology assurance, including hardware upgrades, throughout the agreement. A subscription investment also turns a capital expenditure into an operating expense, which could also help contractors benefit from federal infrastructure spending. Influencing Autonomy Moving forward, OEMs continue to advance machines with more technology, including the addition of integrated temperature sensors, compaction sensors, safety sensors and even GNSS positioning. At the same time, operator assist functionality such as 3D machine control steering and other advancements in machine automation are a focus area for machine control providers and OEMs. These organizations are building new lines of machines that will be capable of more autono- mous features, either by adding aftermarket technology designed for that purpose, or delivering "technology ready" applications. and taking up stringline. Facilitating Adoption However, autonomous construction – and specifically removing an operator or overriding the operator – is a hot and emerging technology direction but is likely many years out. For now, the advantages derived by automatic and semi-autonomous operations are clear, helping contractors greatly improve productivity, manage labor shortages, more efficiently use materials and deliver higher quality products.
VICKI SPEED is a freelance writer covering the construction industry.
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csengineermag.com
May 2022
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