Building Information Modeling is not just for vertical construction. Tunneling projects implementing BIM are realizing benefits in planning, design and construction coordination. In the New York City region, where tunneling projects have become one of the biggest economic drivers for the construction industry, experts are looking at underground jobs from around the country to determine where and how BIM was implemented effectively.
Still, using BIM on tunneling projects is still more the exception than the rule.
“A lot of civil engineering processes traditionally have been done in 2D with very little 3D conceptualization”, says Rolando Mendoza, director of consulting for Los Angeles-based Gehry Consulting, which is using BIM on the expansion of Mexico City’s metro system. “It’s more a cultural thing. They haven’t seen the need for 3D.”
Tunneling construction is a relatively sequential process, usually involving single contractors working in series, says Jon Anunson, regional BIM leader, URS Corporation, Grand Rapids, Mich. “The strengths of a BIM process have the most impact when coordinating multiple trades and contractors onsite.”
“You have to make an informed decision upfront if BIM is worth the effort,” says Jay Mezher, design visualization manager for PB in Seattle, which is currently using BIM on the Alaskan Way Viaduct Replacement. The AWV project involved many disciplines: civil, MEP, HVAC, lighting and architecture, trying to fit all the required components in the tunnel. “We couldn’t have done it in the time we did without the model.”
Jim Palmer, senior vice president for transportation, Hill International, Marlton, N.J., believes there are major economies to be realized by digitizing the whole design and construction environment. “But the things stopping that from happening are institutional.”
Delineating liability profiles between designers and contractors is a big issue. “The AIA and contractors have addenda to deal with liability, but that is really for vertical construction,” Palmer explains. “The market has not really sorted through potential liability issues particularly in horizontal construction.”
Most horizontal construction is public works through government agencies. These agency’s delivery methods often don’t permit the integration between design and construction teams required to get a lot of benefit out of 3D construction, Palmer says. “Once you start integrating your teams and crossing your traditional liability lines, you are creating risk for yourself. Public owners are more concerned about capping risks than reducing costs.”
Where it’s Working?
In Seattle, the Alaskan Way Viaduct Replacement (AWV) project showcases the benefits of utilizing BIM to design and construct large, complex tunnels. The Viaduct, a two-tiered elevated highway built in the 1950’s, is the main north-south highway through Seattle. In 2001 the structure was damaged in an earthquake and subsequently repaired.
Due to the structure’s age and susceptibility to earthquake damage, city, state and county officials starting exploring alternatives for replacing the AWV with a new elevated structure or tunnel in 2004. The Washington State Department of Transportation enlisted Parson Brinckerhoff , New York, to create visualizations of the alternatives.
PB developed 3D models of the options along with the existing above-ground and subsurface structures in the area, including buildings, roads, utilities, and piles.
Animated visualizations developed from the models communicated the design proposals to the public showing what each option looked like, what it would be like driving along the proposed alignments and how each option might impact property owners, says Gordon Clark, PB’s chief engineer on the project.
As detailed information in the models expanded, simulations helped stakeholders evaluate options, hone the design process and make informed decisions, Clark explains.
Construction schedules linked to the models enabled simulations of how construction sequencing impacted traffic and adjacent properties. Modeling of tunneling components, such as MEP systems and emergency access, facilitated design coordination and permitted the team to use space proofing and clash detection to identify interferences between components.
“When you can see it visually in one model it helps show how things get built, if there is enough space for everything and if everything is located in the best place in the tunnel,” says Ron Paananen, WSDOT program director.