Construction of Sound Transit's East Link light-rail tunnel has reached 30 percent completion, according to the transit agency. Excavation is expected to progress at approximately three to four feet per day.
Sound Transit is utilizing Sequential Excavation Method (SEM) to build the tunnel due to the short tunnel length and to minimize the impact of tunnel construction on neighboring homes and businesses. Sound Transit explains that SEM removes soil in small sections or bites using an excavator and support equipment. As soon as soil is removed, shotcrete is sprayed on the tunnel's perimeter and lattice girders made from steel reinforcing bar provide additional structural support for the tunnel.
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