Numerical Simulations of Fourth Avenue Landslide Considering Cyclic Softening

Abstract

Cyclic softening of fine-grained soils poses a significant hazard to geotechnical infrastructure in many parts of the world. Methods to numerically evaluate the cyclic softening and subsequent localization behavior in clays in practice are less developed than techniques to model liquefaction-induced strength loss of granular soils. The PM4Silt constitutive model can model the dynamic response of low-plasticity silts and clays while being relatively easy to calibrate and use. This paper investigates the ability of PM4Silt to model earthquake-induced deformations caused by strain-softening of a mildly sensitive clay. The Fourth Avenue landslide that occurred in Anchorage, initiated by the 1964 Great Alaska Earthquake, is used in this evaluation. Results from previous studies are used to estimate site stratigraphy and relevant soil properties. The model calibration procedures and results are discussed. Simulation results using PM4Silt are compared with the observed displacements and results from previous studies using different constitutive models. The effects of different model calibrations are studied, as well as the influence of input motion and mesh density. The results demonstrate the PM4Silt is able to capture the general response of the Fourth Avenue landslide, although the results are sensitive to the input parameters and show some dependency on mesh size.