recalls Jason Hardell. “We talked to a few different welding equipment manufacturers early on and came up with this system.” Two sections are placed on an automated roller assembly, joined, full penetration welded in several passes, and ultrasonic tested to verify strength. The completed full-length casing was trucked to the shoreline and shipped to the BG 55 barge for installation. The welding system proved to be an effective alternative to workers doing the job by hand. “You're doing a full penetration V-shaped weld on a one-inch casing,” says Rob Harms. “It's a serious welding job.” Specially Designed Conventional Tools ECA and Harms chose conventional tooling for the BG 55 during the pre-bid phase. “We chose to drill with a lockable Kelly bar combined with BAUER tools including double-cut rock buckets and a cleanout bucket,” says ECA’s Gordian Ulrich. “For better guidance, verticality, and production reasons we designed and built these tools extra-long and equipped them with BETEK bullet teeth.” Drilling up to 240 feet with a telescoping four-section Kelly bar was no easy task. This 84-meter (275.5-foot) bar is custom-made for the BG 55. It is among the largest of the few that exist in the U.S. and the lon - gest ECA has sold. “The telescopic Kelly bar is like a long asparagus- type bar; the longer you extend it, the more it tends to wobble,” says Ulrich. “When you crowd down on the bar the tip tends to take the path of least resistance below the casing, so putting the right tool on it and having well trained operators are key factors in the drilling success.” The project had a tough vertical tolerance spec of 1.5 percent. Harms purchased Kelly bar stabilizers BAUER had used on several other deep holes around the world, but the skill of its operators in combination with the specially tailored tools made them unnecessary. The tolerance was achieved starting with the first drilled shaft. Harms had no regrets because being prepared up front was better than shutting down the project for months while tooling was manufactured. Building the Foundation for Progress Harms is on track to complete this roughly 4 ½ year project on sched - ule. It will then pass the torch to the phase two contractor to construct the lift bridge and flanking spans superstructure, communications, and signal and overhead catenary work. The old bridge will be demolished and rail traffic will be transferred to the new structure in phase three. “The drilling rig (BG 55) is really what’s driving the job,” says Rob Harms. “The shift from two 12-hour shifts to three 8-hour shifts really made a difference. It’s going really well.” Building a foundation for a structure of this size and complexity is a challenge regardless of the construction method chosen. In the case of the Raritan River Bridge, Harms combined innovation, teamwork, pre-planning, vendor partnerships, and the right equipment to make the project a success.
spoils were loaded into a hopper barge by excavator and transported to the shoreline for disposal. Workers spliced the galvanized rebar cages on an adjacent barge. Once completed, the crane hoisted them into the casing. The shafts were com - pleted with the pumping of 4,000-psi Self-Consolidating Concrete (SCC). Harms also used its BAUER BG 40 for backup. The rig was positioned on a pile-supported trestle to Kelly drill the shallower shafts near the shoreline. The Trains Kept Rolling Passenger trains chugging past the Harms barges were a constant reminder of the challenges of working next to an existing bridge. Drilling 240-foot shafts in proximity to an active railroad requires caution and finesse. Project specifications required Harms to complete the shaft concrete within 36 hours from when drilling advanced below the permanent cas - ing. “We had to drill it, clean it out, get the rebar in, and fill it as quickly as possible,” says Rob Harms. “The potential for collapse increases the longer you leave the hole open so we had to move quickly.” Vibration was also a concern. Reducing it is why drilled shafts were chosen over driven piles. Harms installed and monitored vibration sen - sors on the existing bridge for safe measure. Harms equipment operators, namely for the BG 55 and crane, had to work carefully to avoid contact with overhead lines on the existing bridge. The wires carried up to 38,000 volts. Working from barges in a windy area further complicated matters. Transporting, Prepping, and Handling Casing Casing was sourced from Illinois. Fabricators that can produce sec - tions up to 143 feet in length with the ability to roll one-inch walls are uncommon. The fabricator and supplier Nucor Skyline shipped the casing by rail and truck in 75-foot sections. Harms needed a way to assemble them on site. “We set up a semi-automated shop to weld the sections quickly,” Members of the ECA and Harms teams are pictured with the barge-mounted BG 55 on the Raritan River Bridge project.
BRIAN M. FRALEY , Fraley Construction Marketing
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June 2022 csengineermag.com
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