ABSTRACT
ABSTRACT: This study consists to estimate the risk (potential) of liquefaction of a saturated soil deposit (sand) when it is subjected to horizontal seismic excitation at its base using the total stress approach. This approach requires the determination of the shear stress developed by the seismic loading (τa) necessary for the calculation of the report of cyclic stress (RCS) and the evaluation of the cyclic shear resistance of soil (τd) necessary to estimate the report of the resistance cyclic shear (RCR). For the computation of RCS, we used two methods, the simplified method of Seed and Idriss using an empirical formula, and the equivalent linear method with concentrated masses in order to adjust (iterative procedure) the shear modulus and damping factor according to the level of shear deformation because the stressstrain diagram of the layer is non-linear with energy dissipation by hysteresis in each cycle. For this reason, in this study, the behavior of the soil had been represented by the hyperbolic relation of Masing. For the determination of RCR, the methods of Robertson and Wride and Seed and Idriss based on the in-situ test CPT were used. The ratio of the two constraints permits the determination of the safety factor against the risk of liquefaction (FS). To calculate Fs, we used for the SPT soundings on the one hand the simplified method of Seed and Idriss to calculate RCS and that of Blake’s method for estimating RCR for the soundings where N160 < 30 and other hand the dynamic method for determining RCS associated with the method of Youd and Idriss to evaluate RCR for the soundings where N160 > 30. For the CPT soundings, the formula of Seed and Idriss associated with the CPT methods cited above were applied. And finally, a risk map will then be proposed for visualizing risk areas using a Geographic Information System (GIS).
