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December Dinner Meeting
December 15, 2016 @ 5:30 pm - 9:00 pm
Beacon Hill Station and Tunnels, State of the Art Underground Construction in Difficult Ground
The Beacon Hill Station and Tunnels contract includes the civil facilities construction for approximately one mile of 20-foot diameter twin-bore tunnels, and a deep, mined, binocular tunnel station. The mainline tunnels were driven using an Earth Pressure Balance Tunnel Boring Machine (EPBM) and a one-pass pre-cast segmental lining. The Beacon Hill Station is the deepest mined transit station in soft ground using the Sequential Excavation Method (SEM) for tunnel structures up to 40 feet in diameter in North America.
The Beacon Hill station and tunnels were constructed in a very complex geological setting influenced by several glacial and non-glacial periods and possible tectonic influences. In 2002 and 2004 the US Geological Survey redefined the aerial extent of the fault splays and interpreted a “deformation zone” for the Seattle Bremerton Fault, such that the Beacon Hill Station is within the deformation zone and ½ mile north of the northern-most fault splay.
Due to the engineering complexities and safety considerations associated with the tunnel construction, the Beacon Hill contract provided for a range of options for the contractor to respond to unforeseen conditions in a timely manner with cost allowances for these measures included in the base contract bid price.
“Red” Robinson, Vice President of Shannon and Wilson, will discuss the geologic conditions anticipated and subsequently encountered, how the actual conditions were handled, and the overall construction of the station and tunnels.
ROBERT A. “RED” ROBINSON, C.E.G., R.G.
Senior Vice President of Shannon & Wilson, Inc.
Director of Underground Services
Robert “Red” Robinson is Director of Underground Services at Shannon & Wilson, Inc. and has over 40 years of experience on geotechnical assessments and design for over 400 tunnels throughout Central and North America. He has participated in the design and construction of a wide variety tunnels constructed in soil and rock ranging from 3-ft diameter directionally drilled utility lines to the world’s largest diameter soft ground tunnel at 64 ft I.D. for Interstate 90 in Seattle. He has published over 60 technical papers on various aspects of geotechnical exploration, design, construction, and construction monitoring for tunneling and has been active on several U.S. and international geotechnical and tunneling committees. Currently Red is involved with a variety of transportation and utility tunnels including: the 58-ft excavated diameter Alaskan Way Viaduct replacement tunnel in Seattle, Regional Connector and Westside Corridor Sections 1 and 2 in Los Angeles, and the Lower and Middle River Des Peres CSO Project in St. Louis.
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