Numerical Simulations of the Fourth Avenue Landslide Considering Strain-Softening: Fid-Bau Portal

Numerical Simulations of the Fourth Avenue Landslide Considering Strain-Softening

Kiernan, Michael / Montgomery, Jack

Cyclic softening of fine grained soils has led to significant damage to structures in previous earthquakes. Despite this, methods to evaluate the potential deformations due to cyclic softening are not as well developed as methods to evaluate potential deformations due to earthquake-induced liquefaction. This is especially true for numerical analyses where clayey soils are often modeled using a single undrained strength without considering the potential for strength loss. When strain-softening is considered, the solution may become mesh dependent leading to unreliable results. This paper explores the use of a constitutive model that can account for strain-softening while providing an approximately mesh insensitive solution. The formulation of the model and softening-scaling approach is briefly described. The model is then used to analyze the case history of the Fourth Avenue landslide which has occurred due to cyclic softening of the Bootlegger Cove clay (BCC) during the 1964 Great Alaska earthquake. Results from previous studies are used to characterize the stratigraphy at the site along with the strength of critical layers. Results from numerical simulations using the strain-softening model are then compared with the observed displacements at the site. Uncertainty due to the choice of the input ground motion and the material properties are explored along with the effects of changing the density of the mesh.