PSI - Issue 78

Nadia Salvatore et al. / Procedia Structural Integrity 78 (2026) 81–88

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response analysis was not feasible. As a result, the liquefaction assessment post-treatment was conducted using the same seismic input PGA as before.

Fig. 2: Schematic geological cross section of the area of Cherry Hill. The topographic profile is extracted from the 5 m DTM of Davis County; the map on the left shows the position of the cross section; the yellow lines depict the extension of the lateral spreading deposits (modified from McDonald and Ashland, 2008); the red diamond represent the Cherry Hill Interchange; the blue line represent the trace of the cross section; the red line approximated the surficial trace of the Weber segment of the Wasatch fault (modified from USGS https://usgs.maps.arcgis.com/apps/webappviewer/index.html?id=5a6038b3a1684561a9b0aadf88412fcf). The wedge between the triangular facets and the Bonneville and pre-Bonneville sediments at the footwall of the Wasatch fault was intentionally left blank due to the uncertainties on the amount of the fault displacement. To analyze the potential for ground motion amplification and quantify the PGA value corresponding to the foundation depth of the viaduct, a site response analysis was conducted using the 1D nonlinear time domain DEEPSOIL code version 7.1 (Hashash et al., 2024). According to the 2018 National Seismic Hazard Model for the conterminous United States, a PGA value of 0.6 g at seismic bedrock was estimated considering a 2% probability of exceedance in 50 years and a NEHRP site class B/C (V S 30 = 760 m/s). Four natural accelerograms (Fig.3b) were selected in accordance with the seismological characteristics (expected magnitude and source-to-site distance of the extensional regional fault systems), and scaled to the input PGA value of 0.6 g by ensuring a scaling factor lower than 4 (Pagliaroli and Lanzo, 2008). Subsequently, the seismic input was applied at the seismic bedrock (characterized by V S = 760 m/s) located at a depth of 200 m as deduced from data from previous studies acquired in Level 1. Above the bedrock, the stratigraphy beneath the viaduct primarily consists of silty sand and sandy silt, with clay being predominant in the first 2 meters from the surface (Price et al., 2000). There are also intercalations of coarse material resulting from the alternating transgression and regression of Lake Bonneville, leading to the deposition of fluvial deposits, such as the Weber delta. Ground motion amplification effects were modeled through a total stress site response analyses based on three stratigraphic logs, which are considered representative of the geological and geotechnical conditions along the viaduct. The V S profiles used in the analyses, shown in Fig. 3a, correspond to the power function that best approximates the measured values, extending the VS profile up to a depth of 200 meters. The analysis did not consider the improvement in the upper 15 meters of subsoil. The hyperbolic MKZ model with non-Masing rules was employed in the modeling, while the nonlinear soil behavior was characterized using Darendeli (2001) normalized shear modulus and damping curves for a plasticity index PI=0. The results, in terms of PGA profiles, are presented in Fig. 3c, indicating a deamplification due to the high level of nonlinearity experienced by the soft soils under severe seismic input. An estimated PGA value of 0.2 g at the top can be derived from the average PGA profile (dashed red curve in Fig. 3c).