|DIALOGUE Barrington Bridge meeting is one of many in Northeast to change process.|
The use of drilled shaft foundations is growing nationwide, prompting many industry leaders to say state highway specifications are flawed, outdated and lead to claims and lawsuits. To develop a dialogue between industry and the public sector, the Northeast Chapter of the Association of Drilled Shaft Contractors has been meeting with state officials to help improve design criteria.
"We're not saying drilled shafts are the answer to all foundation needs," says John Roma, vice president of New England Foundation Co. Inc., Quincy, Mass. "But when shafts are used, we are finding outdated concrete specifications on slump, flow through rebar cage, obstructions, rebar spacing and load testing that are causing needless problems. It is in the public interest to establish good practices for drilled shafts." He notes, for example, that many specs typically call for 6-in. slump for concrete, but tremie-placed concrete needs 8 in. to 9 in. Similarly, aggregate is being specified too large to flow through tight, seismically designed rebar cages used in shafts.
"Construction workmanship and quality issues also have been discussed, but the overall goal is to improve the quality of and ensure the uniformity of drilled shaft foundations," says Peter Osborn, national geotechnical engineer for the Federal Highway Administration in Providence, R.I. He is a leader in the Northeastern States Geotechnical Engineers, an ad hoc group of public agency engineers that meets with ADSC. "Currently, we're looking at the variability of regional specs and concrete mix design," he says.
The groups also have discussed problems concerning contractor prequalification, mobilization pay and pay for obstructions. "In many instances, state specs require a certain level of competence to drill shafts. Yet after contracts are awarded, many general contractors decide to self-perform the installation," says Martin McDermott, engineering geologist with McKinney Drilling Co., Colmar, Pa., and ADSC Northeast Chapter president. "If the states would just enforce the qualifications provision, many problems could be avoided."
"Some design issues we can resolve, others may be code based and need national attention," says Leo Fontaine, a transportation engineer with the Connecticut Dept. of Transportation. "Bad specs require statewide education."
Some of the issues arose at a Jan. 23 constructibility meeting in Providence where officials from Rhode Island DOT, FHWA and ADSC discussed using drilled shafts in lieu of battered piles for the new Barrington Bridge, a 626-ft-long, two- lane, prestressed box-girder structure. It must keep the same look and alignment as the original and will be bid mid-year.
The dialogue is unique. "This process has happened in individual states, but never in a region and could serve as a national model," says S. Scot Litke, ADSC executive director in Dallas.