Evaluation of a Simplified Soil Constitutive Model Considering the Implied Strength and Porewater Pressure Generation for 1-D Seismic Site Response

Porewater pressure (PWP) generation leads to soil softening and potential liquefaction of sandy soils during earthquakes, and can decrease ground motion amplitudes at high frequencies and increase the predominant period of shaking. This paper presents an evaluation of the generalized Quadratic/Hyperbolic constitutive model (Groholski et al. 2016) coupled with two PWP generation models, termed GQ/H+u, as implemented in DEEPSOIL V 6.1 (Hashash et al. 2016). The GQ/H+u model can represent large-strain shear strength and thus provides more realistic response at liquefiable sites where large strains are expected. First, sets of cyclic direct simple shear tests were used to evaluate the models. Comparisons of measured and computed stress-strain loops and excess PWP generation illustrate that the model reasonably captures measured cyclic stress-strain and PWP responses. The GQ/H+u model also can reasonably capture acceleration time histories and response spectra measured in centrifuge tests in loose and dense sands subjected to strong shaking.