The Hanford Viaduct will span nearly 1.2 miles over major existing
roadways and rail lines. The bridge is large enough to be split
into two projects. Forefront is working on the south end of the
bridge, where 1,290 14-inch square concrete piles are required for
the 17 footings of the section. The northern end needs somewhere
close to 6,200 piles.
The 90-calendar-day deadline to complete this work makes for
long days and six-day weeks for the Forefront crew.
The company is using two rigs on the project to drive the 40- and
45-foot concrete piles. The first is a Link-Belt 218 110-ton crawler
crane with a D46 impact hammer from American Pile Driving
Equipment with swinging leads. The second pile driving rig – and
this one is uncommon on the West Coast, says Jeff Bird, president
of Forefront – is a Junttan PMx28, with a Junttan HHK 7S hydraulic
hammer. Bird is pleased with the effectiveness of the Junttan
hammer, a piece of equipment that’s fairly new for the company.
He believes this bridge work is the first time Junttan machinery
has been used in such an application in California, as the Finnish
manufacturer is not yet a big player in the West Coast market.
In an effort to ensure the project moved forward on schedule,
the California High-Speed Rail Authority (CHSRA), which is
responsible for overseeing the planning, designing, building and
operation of the system, chose to release casting of the concrete
piles for the viaduct structure prior to the final lengths being
determined. While this may have allowed the pile driving portion
of the project to commence in early 2020, it created a challenge
for Forefront.
The pile cutting challenge and solution
Once the test piles were installed (one for each of the 17 footings
on the southern portion of the bridge), it was determined that the
precast piles were longer than required. Consequently, all of the
installed piles had to be cut, ranging from three to eight feet.
The company’s first plan was to cut off the bottom of the piles
prior to installation, but the CHSRA designers decided against this.
As a result, the only option Forefront had was to cut off the tops of
the 1,290 piles after installation.
With the 90-day deadline in mind, Bird’s team needed to come
up with an efficient and safe method to break the concrete on the
piles; the traditional chipping gun method would be slow and hazardous
for Forefront’s crew members.
“Due to the massive quantity of piles to be cut off, we had to
think outside the box in order to get this done safely and efficiently,”
said Bird.
Bird is excited about the solution the team developed: “It
will save us a lot of time,” he said. The Forefront team came up
with a two-stage process for cutting the piles. First, it will use a
custom-made machine by Aggregate Technologies that has jaws
to support the pile and a saw to cut off the piles approximately
2.75 feet above the final cut-off elevation. Second, the team will
use a pile “crusher” to expose the rebar extending from the top
of the piling.
The pile crusher, manufactured by Unidrill, will run off the
hydraulics of, and be suspended from, an excavator. (Forefront
encountered an unexpected logistical challenge as the coronavirus
outbreak in China delayed the machine’s delivery, but it arrived
before the cutting operation was scheduled to begin.)
The company is also doing what it can to be environmentally
friendly on this project and elsewhere.
“We use biodegradable vegetable hydraulic oil in the power unit
when we run a drill and auger for pre-drilling to avoid any environmental
impact in the unlikely event of a spill,” said Bird. In addition,
“all concrete and steel debris from cutting piles is transported to a
recycling facility, and to limit emissions on the job site, engines are
turned off instead of idling when they’re not in use.
“Our company philosophy is to look at new technologies and
make use of them to be as efficient as possible,” said Bird.
This is evident in Forefront’s use of the Junttan equipment, the
Aggregate Technologies concrete-cutting saw and the Unidrill pilecrushing
machine on this single project.
“We can get the job done more efficiently, more economically
and more safely,” he said, “by exploring non-traditional options.
Hence our name, Forefront. We like to say we are living up to
our name.” t
PROJECT SPOTLIGHT
“Due to the massive
quantity of piles to be
cut off, we had to think
outside the box in
order to get this done
safely and efficiently.”
– Jeff Bird, Forefront
Deep Foundations
78 | ISSUE 2 2020 www.piledrivers.org
/www.piledrivers.org
