Show Me the Savings
How machine control saves time for a contractor in Missouri
A Missouri contractor says using an automated machine-control system on a trimmer and a paver is saving approximately 10% of the time required to build a $16.7 million highway project.
Ideker Inc. won the State Highway 45 project to build three miles of concrete pavement through a commercial and residential area in Parkville, MO. The Missouri Department of Transportation (MoDOT) specified that Ideker remove the old two-lane asphalt pavement, regrade the project, and place four lanes of new concrete pavement. The contract also includes building a 10-foot-wide bicycle path and walkway on the south side of the new highway.
Once the utilities were relocated, work began in the spring of 2011 with clearing the right-of-way to widen the roadway. With that complete, Ideker built a 1-mile stretch of temporary asphalt pavement on the north side of the road to carry traffic while removal and replacement proceeded on the eastbound lanes. MoDOT required that two lanes of traffic be maintained during construction.
Because the old asphalt pavement was only 6 to 8 inches thick, Ideker chose to tear it out with a Caterpillar 330 excavator. “You have to run it through a crusher to recycle it anyway,” says Dan Tarr, Ideker project manager. “So instead of milling it out, we are just chunking it out with our excavator and hauling it to our asphalt plant. There is no concrete under the asphalt.”
The entire 3-mile project requires excavation of some 225,000 cubic yards of earth, says Tarr. “It is an unusual project in that there is not much right-of-way,” says Tarr. “It is a tight project and some fills are 30 feet deep but not very wide at the top. We may only add 12 feet at the top. In other locations we might go out to 35 feet.”
Mass excavation proceeded with a Caterpillar 345 excavator, two 30-ton Volvo articulated trucks and on-road trucks. “We cut out the hills and fill in the fills,” says Tarr. “Some hauls are within 500 feet, and for other hauls we load dirt into on-road dump trucks and haul it a mile-an-a-half to 2 miles. We’re using three to five on-road dump trucks; most of them are tri-axle Kenworth units.”
Grading and paving began with a 1-mile section of eastbound lanes. Ideker used a Caterpillar D6R dozer fitted with a Trimble GPS to bring the grade to within one-tenth foot. To fine-grade the subgrade, a Gomaco 9500 trimmer fitted with a stringless Leica machine-control system swung into action.
A robotic total station, positioned within 500 feet of the trimmer, could “read” the trimmer’s position. Then the total station communicated the actual position of the trimmer back to a computer onboard the machine. The onboard computer contained a digital terrain model of the proper grade for the project, and the computer could compare the trimmer's actual position to the design model. Based on the differences between the actual position and the design grade, the Leica system adjusted the steering and cutter elevation of the trimmer. “We trimmed the subgrade to accuracy of less than one-hundredth of a foot,” says Tarr.
For compaction, the primary machine was a Caterpillar 815 pad-foot roller. The project also required a 4-inch-thick aggregate base, again trimmed with the stringless Gomaco 9500.
We asked Tarr how he likes the stringless trimmer. “I don’t know how you wouldn’t like the stringless system,” he said. “You pull up on the job, you unload the trimmer, and you are trimming.” He says Ideker employs a surveyor who builds the digital terrain models for stringless work.
After the first 4,200-foot section of eastbound lanes is graded and paved, Ideker will go to work on the remaining 2.2 miles of roadway. The contractor will pave the two eastbound lanes completely through the project, then switch traffic onto them, and grade and pave the west-bound lanes. Construction was scheduled to start on the westbound lanes immediately after July 4, 2012.
How does your production stack up to this?
|A Leica Total Stations helped the Gomaco 9500 Trimmer with one-hundredth-of-a-foot accuracy.
New Dozer Breaks the Record
Every minute counts when you’re building the parking lot for a Home Depot warehouse distribution center. The big box building is substantially complete, and they’re installing equipment. You’re working for a general contractor who wants to turn the facility over to the owner as soon as possible. “We are always the last ones in there with the least amount of time to do our aspect of the work,” explains Chris Wirkus, general superintendent for Gallagher Asphalt, in Thornton, IL.
Wirkus and his crew are charged with grading the subbase, spreading base stone, and laying the asphalt for the Home Depot truck parking lot at the Center Point Intermodal Yard. It’s located in Joliet, IL, and the truck parking lot is huge: 111,000 square yards, or about the size of 17 NFL football fields.
Time is also tight for Gallagher because labor costs in the Chicago area are among the highest in the country. So if new technology and equipment can speed construction, Gallagher is definitely interested. That’s why the contractor is trying out a new 764 High Speed Dozer from the John Deere dealer.
“We acquired the 764 High Speed Dozer because it gives us the potential to boost our productivity,” says Jim Trost, superintendent of operations for Gallagher. “With the cost of labor in this area, anything we can do to improve our productivity will give us a competitive advantage.”
The High Speed Dozer has proved its value, say the folks at Gallagher. In fact, one day last summer it set a company record in base stone placed in one day: 13,100 tons in 12 hours. The previous record of 12,000 tons was set several years ago. That time, a conventional dozer and a motor grader—two machines—were required to reach the 12,000-ton level. The 764 High Speed Dozer spread all 13,100 tons by itself.
“The first day of spreading stone we did 7,100 tons,” says Terry Sullivan, project superintendent for Gallagher at the Home Depot project. “As we saw what the High Speed Dozer could do we doubled our trucks and ended up laying over 13,000 tons on the second day.”
Wirkus recalls it well. “We had 38 trucks hauling the CA6 road mix (base stone) and each truck could make approximately two rounds per hour. That put us up to a production level of just a little over 1,000 tons per hour that we were able to dump, place, and compact.
“Using the 764 High Speed Dozer, we would sometimes have eight trucks in a line dumping at the same time,” says Wirkus. “The 764 was able to keep up with those trucks by pushing the piles down and getting them very close to grade. You just dump a pile, and the 764 powers right through it.”
Previously, when using a motor grader to spread stone, Gallagher’s trucks would have to use chains to restrain the tailgates, dumping gradually as they moved across the grade. But it’s faster for each truck to dump all in one place, then use the 764 High Speed Dozer to spread the stone.
“With the High Speed Dozer they can take the chains off the trucks and dump the whole load,” says Sullivan. “The dozer pushes right through it. As far as bombing in stone like we’re doing here, there is no comparison. The 764 will beat a blade hands down!”
Wirkus says the 764 is quick on its feet. “The 764 is very maneuverable around structures and light standards,” he says. “The dozer has a lot of power and for your long runs the 764 just backs up so fast. I mean, it is a very versatile and powerful machine.”
It’s a one-of-a-kind machine. John Deere says the articulated frame steering and a purpose-built four-track oscillating undercarriage are what makes the 764 so maneuverable. And long-life rubber tracks enable it to traverse pavements with no damage to the surface.
Gallagher has equipped the 764 with an integrated grade-control system, which helps the machine cut to grade far more quickly. “With the GPS you cut down on your labor because now you don’t have to have people pulling stringline every 50 feet,” says Wirkus. “That could take two or three workers, which in this area are very expensive. So the grade-control system is a huge advantage.
Although the 764 can pull implements such as a roller for compaction, Gallagher does not do that. “The dozer is too fast. We back up too much with it,” says Wirkus.
Gallagher’s operators approve of the visibility on the new dozer. “They like it,” says Wirkus. “We did some training prior to this job, and the operators rave about the visibility.”
Operator Mike Woss is impressed with the quickness of the new dozer. “The hydraulics are very responsive,” says Woss. “I definitely like this dozer.”
Gallagher management is very progressive, says Sullivan. “They’re always looking for new technology to make our lives easier and more productive. And around here, we’re all very impressed with the High Speed Dozer.”
“A No-Brainer To Use”
Using a GPS on one dozer for fine-grading slashes the time a job takes to less than half the time the same machine would need without a GPS, says Steve Blair, chief executive officer at Feutz Contractors Inc., in Paris, IL.
Since September 2010, Feutz has been working on a $6 million contract to rebuild 3 miles of County Road 18 in Coles County, IL. As of late last August, the contractor was on track to beat the scheduled deadline of December 23, 2011. “We tore out the old 18-foot chip-and-seal road and we’re upgrading it to 24 feet wide with full-depth asphalt and standard-width shoulders,” says Blair. “Plus, there are two new bridges in this section of roadway.”
Clearing and grubbing came first, along with stripping the topsoil. Feutz removed the old road by ripping it up with a Caterpillar D8. Then, with Caterpillar 621F scrapers, the crew picked up the old material and placed it in the fill.
“This job needed imported fill, so we used two borrow pits alongside the existing roadway,” says Blair. “We used one and sometimes two Caterpillar 345 excavators with mass-excavation buckets on them to work the borrow pits. And we used up to five Caterpillar D400 articulated dump trucks to haul the fill. Hauls ranged from about 1,000 feet to 4,500 feet. The job had 118,000 cubic yards of borrowed excavation, and about 20,000 yards of ditch excavation and other cut-to-fill movement.”
Fill dirt was spread with a Caterpillar D7 that was not equipped with a GPS. Fine-grading came next. “When we got within half a foot, we’d bring in a Caterpillar D6N fitted with a Trimble GPS,” says Blair. “Then we’d take it to within half an inch prior to stabilization with cement.”
The GPS saved more than time, Blair said. “With the GPS you’ve got one operator and one machine,” he notes. “You don’t need two people to set stakes and grade and to do all that work. Certainly the GPS pays for itself.”
“We spread cement with a Stoltz spreader pulled by a John Deere ag tractor,” Blair continues. “Then we used a Bomag MPH 100 to stabilize the cement into the grade.” Compaction followed with a Caterpillar 815 padfoot compactor.
“The asphalt paver had to pave from stringline,” Blair said. “So we set up a stringline and trimmed the grade with a CMI TR 225 single-lane trimmer. Then the asphalt paver paved from the same wire. For the paving we hired a subcontractor, Neco Asphalt Co.”
We asked project superintendent Nick Hutchings how he likes the Trimble GPS system. “I love it,” he says. “I wish we had a few more dozers with GPS. We have a Caterpillar 140G motor grader with a Trimble GPS.
“We didn’t take long to learn how to use the GPS,” says Hutchings. “We went to a couple of training sessions for it. One was hosted by a Caterpillar dealer and another was held by Sitech of Indiana, a Trimble dealer. If you know what you want to do with it, GPS is pretty much of a no-brainer to use.”
Author's Bio: Daniel C. Brown writes on safety and technology in the construction industry.