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Technology
Airfield Work Achieves Mach Speed in Pilot Demonstration
(enr.construction.com)
By Tudor Hampton at Ft. Bragg, N.C.
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| HEAVY
HITTERS The Corps of Engineers is combining high technology
and heavy equipment to speed battlefield airstrips. (Photo
above and below left by Tudor hampton for ENR) |
Two dozen combat engineers arrive on
a remote, abandoned airfield at midnight. They are equipped
with night-vision goggles, a couple of laptops, satellite
communications gear and a few pieces of earthmoving equipment.
In a brief period of 12 hours, they map out the terrain, analyze
the soil, generate 3-D digital designs and specify construction
procedures. A motorized scraper guided by global-positioning
satellites begins clearing grub. A day and a half later, the
airfield is ready for minimal traffic.
Such a feat would usually take a team
at least a week to complete. But the U.S. Army Corps of Engineers
is trying to cut design and construction schedules during
combat by at least 50%. As a result, under way is a $23-million,
six-year research project called Joint Rapid Airfield Construction.
The Corps demonstrated JRAC's capabilities to private vendors,
Pentagon officials and other engineers in the armed services
July 14-15 in Ft. Bragg, N.C.
Alongside an existing 3,500-ft-long, unpaved runway, soldiers
built two 40,000 sq-ft aprons, or parking spaces, for 175,000-lb,
C-130 transporter aircraft in only three days. The trapezoidal
aprons measured 300 ft on the long side, 100 ft on the short
side and 200 ft on the tapered sides. The aprons allow planes
to clear the runway so others can land and take off safely.
Interest in JRAC gained momentum after
fighters faced airfield-maintenance challenges on an austere
outpost's dirt runway during the Afghanistan conflict (ENR
2/25/02 p. 20). The first main goal of JRAC is to support
C-130 aircraft within two days by putting into service what
the Army and Air Force call a "contingency airfield,"
one that is either abandoned or captured, then reconstructed
to handle plane traffic during battle.
A final demonstration in 2007 will take
the project to a next critical objective: contingency support
for heavier, 447,000-lb, C-17s, within the same 48-hour time
requirement. In an effort to validate methods and develop
standard construction protocol, the Corps is sharing its research
with other services and asking for their input.
The project has become a top military
priority because "it directly affects the warfighters,"
said Col. James R. Rowan, commander of the Corps’ Engineer
Research and Development Center in Vicksburg, Miss., where
the JRAC team is based.
The program uses off-the-shelf products,
such as geospatial software and soil-stabilizing polymers,
to push military construction to warp speeds. The work is
part of a bigger transformation happening within the Army
to increase its combat mobility. The U.S. still depends heavily
on allied air bases to launch attacks. But the face of global
warfare is changing. Army officials reflecting on the remotely-located
Afghanistan and Iraq conflicts say they must develop the capability
to deploy troops to a distant site in 10 days, defeat the
enemy in 30 days and relocate to another fight in 30 more
days.
"Our challenge is to go anywhere
in the world," said Gary Anderton, civil research engineer
and JRAC program manager. "Once an airfield site is selected,
it must be operational in 48 hours. Any longer than that and
it wouldn't be considered rapid."
The process is fast and furious. On
July 12, soldiers from the XVIII Airborne Corps, 20th Engineer
Brigade and 412th Engineer Command arrived on site at midnight
and began surveying. They had not visited the site prior to
the exercise. Their gear included night-vision goggles, GPS
tools and Toughbook laptops programmed with geospatial software.
Heavy equipment included a Caterpillar-made
Army dozer, an elevating scraper, a motor grader, a $250,000
Terex reclaimer-stabilizer, a skid-steer loader and a prototype
machine called a Rapid Assessment Vehicle Engineer (RAVEN)
based on Bobcat’s commercially-available Toolcat utility
vehicle. Anderton noted that operators received about three
days of "stick time" to train themselves on the
machines.
RAVEN is a unique vehicle that cost
the Army roughly $175,000 to build. It is air-droppable via
parachute. Once deployed, it roves the jobsite, with or without
an operator, to acquire GPS plot points every two meters.
The data is imported into a geospatial database that is linked
to 3-D design software. In its rear cargo area, the machine
is fitted with a mobile soils-testing laboratory hooked up
to a database of soil profiles around the world. The machine
also has an articulating arm in front that handles multiple
attachments, including an automatic, hydraulically-actuated
soil pentrometer, a hammer-like device that measures the load-bearing
strength of compacted earth.
The topographical design process was paperless. After data collection,
soil analysis and 3-D plans were complete (that took 12 hours
for each apron) the information was imported into GPS computers
mounted in the cabs of the heavy equipment. Each machine had
a digital Trimble controller piped into the hydraulic circuits
that control the blade. All the operator has to do is steer
the machine, according to Anderton. Surveyors programmed the
site’s cut and fill requirements and did not use ground
stakes as reference points. But it wasn't a perfect system.
"We still had a couple of hiccups," said J. Kent Newman,
JRAC physical scientist in charge of soil stability. "The
cut and fill was off a bit, and that increased our construction
time."
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Engineers stabilized the ground on one apron using a 6-in.-thick
topcoat of 3% Portland cement and 3% liquid polymer. The materials
were tilled into the soil using the reclaimer-stablizer machine.
On top of the mix were 580 interlocking mats made of fiberglass
polyester and measuring 6 ft. square. The second apron’s
topcoat featured an 8-in. lift of 4% Portland cement and 0.2%
of 2-in.-long polypropylene fibers. The mix was sealed on
the surface with a liquid polymer for moistureproofing and
dust control. The first apron was complete within 48 hours;
the second was ready after another 24 hours had passed. Both
were designed to withstand 750 cycles of C-130s and achieved
strength ratings of 500% to 600% higher than before.
Thomas Manley II, vice president of government affairs for
Terex Corp., Westport, Conn., says that Anderton’s team
is "pioneering what is required for the military in terms
of expeditionary construction." But similar to how automatic
GPS grading is now migrating into military use—several
years after earthmoving contractors began taking it on in
the late 1990s—it is likely that other JRAC innovations
will find their way into the private sector as well. Says
Travis A. Mann, civil research engineer and digital technology
expert for JRAC, "To have guys moving dirt in 12 hours"
after site selection, "that’s an unbelievable feat."
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