DFI Announces the 2017 Outstanding Project Award Winners
The Deep Foundations Institute (DFI) is proud to announce that two groups have been selected to receive the 2017 Outstanding Project Award (OPA). Berkel & Company Contractors is being recognized for the renovation and rehabilitation project on the Andrew Mellon Building, a National Historic Landmark, at 1785 Massachusetts Avenue NW in Washington, D.C. Moffatt & Nichol, Korea Electric Power Corporation (KEPCO) and ADVACT are being recognized for the installation of tripod suction buckets for an offshore wind turbine foundation project located off the Korean peninsula.
The awards will be presented at the DFI 42nd Annual Deep Foundations in New Orleans, October 24-27, 2017.
The Andrew Mellon Building is a five-story Beaux Arts-style building that was constructed in 1917. As part of the renovation, the service area of the building was expanded from 72,000 sq ft to 100,000 sq ft, and a new basement level was added below the existing foundations. The major challenge for Berkel & Company Contactors was to transfer the load from the existing spread footings to new deep foundations, while preserving the limestone façade and plaster interiors. At each of the interior columns, a modified tieback rig was used in very limited headroom to install four micropiles each with a 100-ton capacity in compression. To support the exterior columns and the continuous wall footing, 55 concrete underpinning pits were constructed and, combined with timber lagging and two levels of temporary tiebacks, were used as the excavation support system during construction of the new basement level. To minimize differential settlement between the interior and exterior columns, 69 cased micropiles that were 7 inches in diameter were installed prior to and beneath the underpinning pits. Once the new columns and foundations were completed, load transfer to the new columns was achieved.
As part of national offshore wind power development by the government of Korea, the construction of a 2.5 GW wind farm about 200 m (655 ft) offshore in the southwestern sea off the Korean peninsula should be complete by 2020. As part of the 80 MW pilot phase, a 3 MW 80 m (262 ft) tall offshore wind turbine was installed in late 2016, and is the first offshore wind turbine using tripod suction buckets as its foundation system. The tower foundation, designed and installed by Moffatt & Nichol, KEPCO and ADVACT consists of tripod suction buckets, each cylindrical steel bucket is about 20 ft and 40 ft in diameter and length, respectively, and was installed in the subsurface soil deposit consisting of interbedded sand and clay layers. The design of the suction buckets followed the procedures specifically developed for very large diameter piles. Instrumentation used to monitor the installation of the suction buckets included water pressure measurements inside and outside of the pile, pile penetration depth into the seafloor using echo sounding and physical measurements, and inclination of the pile using two-way tilt meters. Records indicate that the entire assembly was installed with a final tilt of no more than 0.02 degrees from the vertical.
The OPA was established in 1997 to recognize the superior work of DFI members. The projects were selected by a committee based on size, scope and challenges of the project; degree of innovation and ingenuity exercised; and the uniqueness of the solution to the difficulties of the job.