KOMO TELEVISION STATION EXPANSION SEATTLE, WA Temporary Soil Nail Shoring Wall Fisher Properties (Developer) and Sellen Construction (General Contractor) engaged the design-build team of Golder Associates and DBM Contractors to address complicated loading conditions for the temporary shoring of the 47-ft deep excavation for the KOMO television station expansion. We designed a temporary soil nail wall that successfully underpinned the adjacent KOMO building (seen below), and restrained adjacent monorail pier foundation loads while bringing over 20% cost savings to the project compared to conventional shoring. EXISTING BUILDING SUPPORT DESIGN The proposed KOMO television station expansion consisted of an L-shaped excavation that surrounded the existing television station, creating a 90-degree re-entrant corner condition. The excavation height at the building corner was about 40 feet and the materials consisted of sandy silt glacial till with occasional zones of low plasticity clay. The conditions were ideal for soil nailing. The soil nails to either side of the corner were splayed up to 45 degrees as they approached the corner. As usual, the nail pattern was enhanced by 25% to account for the corner condition. DESIGN FOR MONORAIL PIER LOADING Elevated monorail transit system runs adjacent to excavation with 5-ft to 10-ft diameter foundation piers within 8 feet of the excavation. Each pier applied a lateral shear and overturning moment that resulted in a net 200 kip load being applied to the shoring wall. The close proximity of the monorail piers precluded the installation of many of the production nails in front of the piers. Those production nails that could not be installed in front of the piers were installed adjacent to the piers. Additional nails were also added adjacent to the piers to resist the load applied to the wall. Nail spacings approached 2.5 feet adjacent to the piers. The shotcrete facing was enhanced to 8-inches thick to span across the piers between the nails on either side. Sophisticated soil-structure interaction analyses were performed with the computer programs FLAC and STAAD-III in order to demonstrate the degree of soil arching and the validity of the enhanced facing design.
home firm services projects contacts	Ground Support PLLC 2475 - 152nd Avenue NE Redmond, WA  98052		Phone: (425)376-0177 Fax: (425)376-0277 email: info@groundsupport.com