Source: CalPortland | November 1, 2019
CalPortland has received the Washington Aggregates and Concrete Association’s (WACA) Grand Award for its work on the Alaskan Way Viaduct Replacement Program SR-99 Tunnel.
CalPortland’s executive director Bruce Chattin says: “The Alaskan Way Viaduct Replacement SR-99 Tunnel is an iconic concrete structure and at fifty-seven and a half feet in diameter, is the largest soft bored tunnel shaft in North America. As one of the largest infrastructure projects in the U.S., the replacement of the Alaskan Way Viaduct with the SR-99 Tunnel transformed Seattle’s aging waterfront into a modern transportation corridor.”
The Alaskan Way Viaduct was replaced because it suffered from decades of daily use and was declared vulnerable to substantial damage in an earthquake.
Inside the near 2-mile long concrete tunnel, twin stacked 32 foot-wide roadways carry two southbound lanes atop two northbound lanes. The tunnel features fire detection, suppression and ventilation systems and a security system with closed-circuit TVs.
Throughout the project, CalPortland used pre-cast tunnel segments for the tunnel liner, pre-cast panels for the northbound roadway decks, pre-cast bridge girders at the north cut-and-cover structure and extensive use of cast-in-place concrete for drilled shafts and roadway structures.
Construction of the southbound roadway was done concurrently starting approximately 500 ft. behind the tunnel boring machine, synchronised to keep both tunnel construction and road construction operations in sequence and on schedule. The project required precision timing and placement of 220,000 cubic yards of cast-in-place concrete, 130,000 cubic yards of structural foundations, roadways, walls and decks inside the portals, tunnel and buildings and 90,000 cubic yards of shoring piles, excavation support and temporary structures.
Concrete mixer trucks were retrofitted with equipment to reduce emissions and nearly 100 variations of concrete mix designs were utilised throughout the project.
The award was made at the WACA 2019 Awards for Excellence in Concrete Construction, at the Hyatt Regency Seattle.
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