Evaluation of 1-D seismic site response modeling of sand using centrifuge experiments

Abstract

a b s t r a c tThe response of an equivalent 26 m-thick deposit of dry, medium-dense, Nevada Sand with a relative density of 60% is measured in the centrifuge under six 1-D, horizontal earthquake motions applied to the base of the centrifuge container. Several 1-D site response analysis techniques are employed to simulate the experiments, including (a) equivalent linear analyses, (b) nonlinear analyses using a multi-degree-offreedom, lumped mass model, and (c) finite element analyses of a soil column using a pressuredependent, multi-yield, plasticity soil model. An average V s profile was estimated using empirical correlations. Soil dynamic properties included published generic modulus reduction and damping curves with implied strength correction as well as recommended plasticity model parameters based on soil index properties. Computed and measured lateral displacements, accelerations, shear strains, spectral accelerations, and Arias Intensities are presented and their differences are quantified in terms of mean residuals and variance. The comparisons demonstrate that 1-D seismic site response analyses using the available strength corrected, generic, pressure-dependent modulus reduction and damping curves for medium-dense dry sand can reliably compute soil response under 1-D wave propagation using any of the three methods, with an absolute mean residual of less than 0.5.

Validation of a three‐dimensional constitutive model for nonlinear site response and soil‐structure interaction analyses using centrifuge test data

“…To explore the capability of nonlinear and equivalent linear soil models in predicting different response parameters investigated in this study, we compute the residual for each response parameter, as in Hashash et al 26 :…”

“…The sand was pluviated inside the flexible shear beam container of the centrifuge such that an approximately uniform soil layer with a dry unit weight of ρ =1590 kg/m 3 , or a relative density ( D r ) of approximately 60%, could be achieved. The small‐strain shear wave velocity profile of the soil deposit is predicted using the equation proposed by Bardet et al where A =8.811, a =1.935, and n =0.5 are the 3 constants determined for the Nevada sand . The parameters e and p are, respectively, the void ratio and the mean pressure expressed in kPa.…”

“…To explore the capability of nonlinear and equivalent linear soil models in predicting different response parameters investigated in this study, we compute the residual for each response parameter, as in Hashash et al: where X refers to a given response parameter of interest. Figure shows the range of residuals and variances for each analysis type and response parameter—namely, PGA profiles for the far‐field and the structural walls, surface response spectra, surface far‐field Arias intensity, racking displacement, bending strain and pressure profiles of structural walls, and the amplitude of surface settlement.…”

“…where A = 8.811, a = 1.935, and n = 0.5 are the 3 constants determined for the Nevada sand. 26 The parameters e and p are, respectively, the void ratio and the mean pressure expressed in kPa. Figure 6A displays the resulting maximum shear wave velocity profile.…”

Seismic Performance of a Layered Liquefiable Site: Validation of Numerical Simulations Using Centrifuge Modeling

“…These define the outer yield surface and the boundary between the contraction and dilative behavior, respectively. The yield surfaces in the PDMY02 model were defined manually as discrete points for pairs of shear modulus ratio (G/G max ) versus shear strain, in order to describe better the shear stress-strain response (as suggested by Hashash et al 2015). Contractive and dilative parameters were set to reasonably match the simulated results with triaxial tests in terms of stress-strain response and number of cycles to reach liquefaction, as shown in Figures 3 and 4 for Ottawa sand.…”