Liquefaction-Induced Lateral Spreading and Dilative Soil Behavior

During liquefaction, strength and stiffness degradation in sloping liquefied soil may lead to significant cycle-by-cycle shear strain accumulation. Accuracy in quantifying the magnitude of accumulated permanent shear strain is the key to satisfactory modeling of liquefaction-induced lateral spreading. Commonly used stress-space constitutive models may not be easily calibrated to reproduce the observed magnitudes of permanent shear deformation, since the shear flow phase is often accompanied by a minor change in shear stress magnitude. In a newly developed constitutive model, the observed large post-liquefaction shear-strain accumulation is accomplished by introducing a perfectly plastic zone into a multi-yield surface stress-space framework. After the perfectly plastic strain accumulation phase, the tendency for dilation may result in significant regain in shear stiffness and strength. This aspect of soil behavior is also modeled within the aforementioned constitutive model framework. This new model is integrated in an effective-stress fully coupled two-phase (solid and fluid) Finite Element computer code. In this paper, results of numerical simulations conducted using this computational program are discussed. A one-dimensional version of the program is now available on the Internet for on-line execution (http://casagrande.ucsd.edu)