The potential impact of tunneling-induced ground displacements on structures depends on the geologic setting and the nature of the ground surrounding and above the tunnel. This paper summarizes case history data from several tunnels constructed using pressurized tunnel boring machines (TBMs) in glacial soils in Seattle, Washington. A finite element model developed for the Alaskan Way Viaduct Tunnel and calibrated by using the case history data is used to extend our understanding of the condition where looser or softer soil is present above the glacial soils. The results of the finite element model and case history data are used to refine the settlement trough width characteristics for glacial soils for use in estimating settlements using the inverted normal distribution.
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