EXH1105041701

FROM: Jamie Beaver and Allen Jones,Hart Crowser, Inc. RE: BasePreparation Stability Analysis (PhaseII) J-4978-01 CC: Pete Douglass, Peter M. Douglass, Inc. This memo presents the results of our search for soil strength parameters we intend to use in our stability analyses.This memo is focusedtowards evaluating stability of the PhaseII embankment from a subgrade preparation standpoint. Stability analysesfor design of the Phase11and III embankments will be performed under separate scopes of work. Approach to Soil Strength Assignments Assessment We will be analyzing the stability of the Phase II embankment using the program UTEXAS3to provide base preparation recommendations. Our approach to assigning soil strengths will be to use relationships that have been established for soil strength in the geotechnical literature, while considering previous projects at similar sites in the Seattle area as a general guide (Attachment 1). The relationships presented on Figures1 and 2 are strength parameters that have been correlated with standard penetration resistance (SPT)N-values in the literature, and will be used to establish the baseline values for the stability analysis. In general, friction angleswill be assignedto cohesionless soils (sands,sandygravel, etc.). Both shearstrengths and cohesion/friction angle values will be used for both plastic and non-plastic silt/clays. We will use shear strength (undrained) based on SPTN.value to assignthe initial strengths to the fine-grained soil units or embankment fill zones. Friction angle and cohesion will also be used, primarily to test the sensitivity of the model to the strengths of the fine-grained soil units. Our _'L r_j_ Hart Crowser, Inc. J-4978-01 August 13,…

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Call to order – Roll Call – Quorum Established – Land Acknowledgement We would like to acknowledge that our Agency operates in four present-day counties, which are the traditional lands of the Coast Salish people, past and present. This acknowledgement does not take the place of authentic relationships with indigenous communities in our jurisdiction and [...]