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Job Complications Lead To AXIS System Solution
"Various site conditions, including not being able to close the street, and the requirements of other trenchless procedures made it impossible to use other construction methods," said Mann. "We considered microtunneling but the small exit manhole was too small to accommodate microtunneling pilot tubes."
Mann began to investigate other trenchless options. Mann's brother, Patrick Mann, chief operating officer of Magnum Tunneling in Houston, suggested the new Vermeer AXIS system should be evaluated and considered.
Eric Mann contacted Harry Eagle, general manager of Vermeer Mid Atlantic, for information about the system's capabilities. Eagle contacted the Vermeer home office, and ultimately arrangements were made for an AXIS system and the A Team to come to Kannapolis and do the installation as a paid demonstration for Cherokee Construction.
After existing utilities were located and marked, Cherokee crew members closed one lane of traffic leading to the intersection, excavated a 10 by 12 foot launch pit, and cut a hole in the existing manhole that would serve as the exit pit.
The pipe laser then was set in the launch pit at depth and a 1.3 percent grade required by the project. Next, the leveling frame was set in place, the rack assembly lowered into the pit and positioned, and the drill head containing a camera was put in place. Images from the camera are viewed on a monitor at the operator’s console. The rack power unit contains the engine and hydraulic pumps and connects to the rack, powering thrust and pullback of the drill head and casing. AXIS casings are 6½- feet long.
During boring, the cutter bit at the front of the drill head rotates to cut through the soil. With the camera viewing the laser beam on the target, the operator can accurately monitor the target grade and make adjustments if the drill head moves off course.
Keeping the laser dot centered within the cross hairs indicates the drill head is on course with the target grade. Only the cutting bit and center drive shaft rotate as the drill head and casing travel through the bore; the outer section remains stationary as it is pushed through the hole opened by the cutting bit. As the drill head cuts through the soil, the cuttings are simultaneously removed by a high power vacuum system and diverted to a vacuum tank.
Additional sections of drill casing were coupled to the drill head until the head reached the exit pit.