PART 1 Central Artery/Tunnel Project: A Precast Bonanza by Vijay Chandra, P.E. Anthony 1. Ricci, RE. Senior Vice President Chief Bridge Engineer Parsons Brinckerhoff Quade & Central Artery/Tunnel Project Douglas, Inc. Massachusetts Turnpike Authority New York, New York Boston, Massachusetts This article provides an overview of the monumental efforts of Massachusetts transportation officials, their engineering consultants, and multitudes of construction industry professionals to ease congestion, improve motorist safety, and address issues of environmental quality in the heart of Boston, Massachusetts. The Central Artery/Tunnel Project is the largest highway construction job ever undertaken in the United States, involving many diverse types of precast concrete construction. maj or transportation infrastructure undertaking, • Standardized temporary structures utilizing precast con billed as “The Big Dig,” is transforming traffic op crete elements. A erations in and around Boston, Massachusetts. This • Precast segmental box girders integrated into cast-in-place $13.2 billion project, the biggest and most complex trans columns to provide seismically resistant connections. portation system ever undertaken in the United States, is • Precast segmental boxes cut at a skew to connect them on significant not only in this country, but worldwide. Nu either side of straddle bents. merous innovative construction techniques are being used, The project has brought out the best that precast con including: crete technology has to offer — in many cases utilizing • Precast tunnels jacked under railroad embankments. cutting edge techniques — and has been of immeasurable • Deep soil mixing to stabilize land reclaimed from the value to New England’s precasting industry. Precasters, ocean. faced with many complex and daunting challenges, are • Precast concrete immersed tube tunnels. successfully implementing a range of innovative method • Standardized designs for precast New England bulb-tee ologies to make the Central Artery/Tunnel Project a dream girders and slab-on-pile structures. come true. 14 PCI JOURNAL Fig. 1. Central Artery/run nel Project, Boston, Massachusetts. The purpose of the Central Artery! eight hours of congestion each week and Charlestown to the north with a Tunnel Project is to provide an effi day. These conditions were only ex widened eight- to ten-lane under cient, uncongested vehicular route for pected to worsen, to the point that by ground expressway and a first-of- the people of Boston. The city’s exist the year 2010, it was estimated that its-kind asymmetrical, hybrid cable- ing Central Artery, which includes an there would be a 15-hour rush period. stayed bridge crossing the Charles elevated section of Interstate 93 be Massachusetts transportation offi River. tween Congress Street and Route 1 in cials initiated the current Central • An improved 1.7 mile (2.8 km) di Charlestown, is one of the most con Artery!Tunnel Project (see Fig. 1) in rect connection between Leverett gested segments of interstate highway August 1986. As planned, major ele Circle and Charlestown with a state- in the nation. Jammed with more than ments of this extensive project include: of-the-art bridge over the Charles 190,000 vehicles daily — more than Replacement of a 4.3 mile (7.0 km) River. twice the capacity it was originally de segment of the congested Central • A 3.9 mile (6.3 1cm) extension of the signed to handle when it opened in Artery (Interstate 93) between the Massachusetts Turnpike (Interstate 1959 — the Central Artery experiences Southeast Expressway to the south 90) to Logan International Airport, May-June 2000 15 which encompasses a new eight- lane, depressed road passing through a commercial district of South Boston; the new four-lane steel im mersed tube Ted Williams Tunnel beneath the inner harbor (opened in December 1995); jacked concrete tunnels under railroad tracks; and concrete immersed tube tunnels under the Fort Point Channel. A 1.4 mile (2.2 km) South Boston Bypass Road, built in part on an ex isting railroad right-of-way between the Southeast Expressway/I-93 Frontage Road System and the Sea port Access Road. The crucial links, which connect these elements, are the project’s many interchanges. They move traffic be tween the interstate roadways and the major highways, as well as connect to the local road system. Most of the multi-level interchanges are being built while maintaining traffic opera tions on existing interchanges and road ways. Construction within Boston’s confined, highly congested corridors poses unique challenges. This is where precastlprestressed concrete is playing a major role in the construction of the Central Artery/Tunnel Project. Project design began in 1986, utility Fig. 3. Spectacle Island Pier. relocation was initiated in 1991, and Fig. 4. B roadway Bridge under construction. 16 PCI JOURNAL Fig. 6. Slab-on-pile construction. the first phase (which included the The landmark Charles River cable- nents. This has been a significant step connection from 1-93 to Logan Inter stayed bridge has provided a forum for in lowering costs, as has been the de national Airport via South Boston and precast technology for the all impor sign and standardization of precast the Ted Williams Tunnel) opened in tant deck slabs, which utilize both structures using precast piles, precast 1995. The next milestone was the standard and lightweight concrete (see New England bulb tees for the transi connection of Leverett Circle to Fig. 2). Additionally, Spectacle Island, tion structure and precast pile caps, Charlestown via the Storrow Drive an old landfill utilized to dispose of precast inverted T-beams and slabs for Bridge over the Charles River, which some of the project’s excavated mate the slab-on-pile structures (see Figs. 5 opened on October 7, 1999. The en rial, is being converted into a public and 6). tire project is scheduled to be com recreational facility. It will be accessi pleted in 2004. ble by a totally precast pier utilizing NTERCHANGE The Central Artery/Tunnel, the various precast elements such as piles PROJ ECTS largest highway project in American and beams (see Fig. 3). The superstruc history located within a metropolis, tures of the Dorchester Avenue and Two major interchanges built using features: Broadway bridges — part of the 1-9011- the latest technology in precast seg • One of the most extensive uses of 93 Interchange — are also composed mental concrete construction form the precast segmental concrete bridge of precast butted boxes (see Fig. 4). crucial project links connecting inter construction in one location. Major strides have also been made state roadways and major highways. • Widest cable-stayed bridge in the to standardize temporary structures (of These projects are the: world using a precast decking system. which there are over $100 million • South Bay Interchange of 1-90/I- • First hybrid cable-stayed bridge in worth) by utilizing precast boxes, pre 93/Massachusetts Avenue the United States. cast slabs, and other precast compo • 1-93/Route 1 Interchange • First and largest installation of hori zontally jacked precast segmented concrete vehicular tunnels in North America. • Most extensive use of precast seg mental concrete immersed tube tun nels in the United States. • Largest use of the newly developed precast New England bulb tees. • First adaptation of segmental cutting technology in the world. • Innovative development of totally precast slab-on-pile structures. The Big Dig has been instrumental in bringing new techniques and tech nology to the field of precast concrete construction; however, the project has not forgotten more traditional techniques. Fig. 7. South Bay Interchange model. May-June 2000 17 __ __ South Bay Interchange of 1-90/1-93/Massachusetts Avenue The existing substandard inter change at the intersection of 1-90, 1-93 and Massachusetts Avenue, which has limited capacity, is being replaced in stages and expanded to handle a con siderably higher traffic volume (see Fig. 7). The massive new multi-level interchange will be all-directional and include the 1-90 extension to Logan International Airport through the Fort Point Channel and Ted Williams im mersed tube tunnels. The entire interchange, split into four construction contracts, was de signed in both steel trapezoidal and precast segmental concrete box girder alternatives for the viaduct portion. Three of these contracts will be built using precast segmental technology and features precast balanced can tilever and span-by-span construction techniques (see Fig. 8). • Constructing a new four-level inter • Using various erection techniques, The precast segments are being cast change while maintaining traffic op including crane, beam and winch, in western Massachusetts and trans erations on an existing three-level and overhead gantry. ported about 120 miles (193 km) to interchange. the site, as needed, and erected. The • Supporting viaducts on tunnels in erection gantry used for the 1-93 many areas. 1-93/Route 1 Interchange northbound segment was fabricated in • First-time use of concrete segmental The north gateway to Boston Italy and shipped to Boston. Mean box construction in Massachusetts. through Charlestown begins at the I- while, the existing interchange is • Integrating precast pier segments 93/Route 1 Interchange, which is in being demolished in stages as phases with cast-in-place piers to achieve tertwined with the state-of-the-art of the new construction are completed. seismically resistant connections. Charles