This practice-oriented, cycle-counting liquefaction model consists of a linear-elastic perfectly-plastic Mohr-Coulomb model, coupled with an empirical pore pressure generation procedure. Excess pore pressure is generated in response to shear stress cycles, following the cyclic-stress approach of Seed and Idriss. However, the model differs from traditional applications of this approach, where excess pore pressures are computed after a dynamic analysis, as a post-processing step. Instead, the model updates pore pressures continuously during a dynamic analysis, with reduction of effective stresses and shear strengths during shaking. The model has been updated to reflect changes in the simplified procedure, including revised correction factors for initial static stresses and a new shape for the cyclic strength curve. Other modifications include an effective-stress dependent elastic shear modulus, and a switch that prevents shear strength from dropping to residual strength during shaking. Adaptation of the model to 3-D analyses is also discussed. The performance of the model is illustrated with an analysis of the well known Lower San Fernando Dam case history.
- effective stress
Dawson, E. M., and L. H. Mejia. "Updates to a Practice-Oriented Liquefaction Model." GeoCongress 2012, State of the Art and Practice in Geotechnical Engineering. ASCE, 2012.