The Axis guided boring system is a pit-launched trenchless installation method designed to achieve pinpoint, on-grade accuracy while eliminating some of the difficult steps associated with other installation techniques. The guidance system features a laser that determines the line and grade of the bore, enabling on-grade accuracy throughout the process, even in the rock conditions encountered in Olathe.
Outfitted with a tri-cone cutter head, the Axis system led the way, successfully completing several pilot bores up to 450 feet in length and grades ranging from 3.975 percent to just less than 1 percent; necessary to achieve the pitch required to facilitate the sewer’s gravity flow. The varying depths of the many individual sewer lines extending from each home were also a consideration. After pilot bores were completed, a separate crew followed behind using an auger boring machine with disc cutter head to upsize the bore path to the diameter necessary to accommodate the 24-inch HDPE housing. This allowed the crew to jump ahead and keep the project moving forward.
The rolling terrain, which Miki described as a sloping hillside with a fairly significant elevation incline from the launch to exit pits, required one of the bores preparing a launch pit to a depth of 47 feet to accommodate the upward slope of the bore toward the exit pit positioned at 30 feet deep. At these depths considerable shoring was required to secure the walls surrounding the pit.
Among the many features Miki likes about the Axis system is the operator’s ability to know precisely where the drill head is located at all times. The system is equipped with a closed-circuit camera integrated into the drill head that allows the operator to constantly monitor the progress on a screen integrated into the controls console. Corrective steering adjustments to the drill head can be made instantly if needed to ensure desired line and grade is maintained.
“The laser incorporated into the drill head of the Axis system projects onto a screen that has a scope similar to a rifle,” he says. “Even the slightest veer up or down or right to left can be adjusted immediately. Once the pilot bores were completed, upsizing and reaming was a breeze. We used the Axis vacuum system to remove the excess spoil during the reaming process. All the pilot bores were completed on target, on grade and on line. Everything worked really well.”
“There are always concerns when drilling through rock about noise, vibrations, even causing cracks and damage to foundations,” Miki says. “Noise is minimal with the Axis system, however. We had people in the neighborhood come out and ask if we were done already.”