PSI - Issue 78

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

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Fig. 3. (a) Shear wave velocity profile assumed in site response analysis; blue points represent measured values; orange line represents the power function to extend the V S values at depth. (b) Natural accelerograms employed for site response analyses with main characteristics; d epi is the epicentral distance; SF is the scaling factor; M W is the moment magnitude (c) Results in terms of PGA profile for each input motion applied and as average values (red dashed line). Given the seismic input parameters, the liquefaction resistance of the sand site of the Cherry Hill Interchange was evaluated using both Cone Penetration Test (CPT) and Standard Penetration Test (SPT) blow count conducted close to abutment n. 2 and reported by Price et al. (2000). The comparison of the two tests made it possible to assess the liquefaction potential and to evaluate the expected lateral displacement value up to 20 m depth. As suggested by Idriss and Boulanger (2008), the CPT and SPT blow count (q c and N SPT respectively) were first corrected considering an overburden correction factor, and then modified to the equivalent value for clean sand (fine content ≤5%), obtaining the (q c1 ) cs and (N 1 ) 60cs respectively. The Cyclic Stress Ratio ( CSR ) induced by the earthquake can be calculated as originally proposed by Seed and Idriss (1971), considering a PGA of 0.2 g, and the depth reduction factor as defined in Idriss et al. (1999). To make the data comparable regardless of the earthquake, W is standardized to the value of 7.5 using the Magnitude Scaling Factor given by Idriss and Boulanger (2008) and a design magnitude of 7.4 (Rollins et al., 2012). The Ground Water Table was considered at 4 m depth, using an average value of measured GWT level in the area. The CRR and the factor of safety (FS) were calculated as proposed by Idriss and Boulanger (2008) for both CPT and SPT, while the Liquefaction Potential Index (LPI) is calculated as in Iwasaki (1978). The results are shown in Fig. 4 b, c, and d. For a liquefiable layer measuring 14 m (estimated from SPT analysis), the potential lateral displacement was estimated using both the Lateral Displacement Index (LDI) as described by Zhang et al. (2004) and the predicted lateral displacement (DH) proposed by Youd (2018). The resulting value ranged from 2.8 to 3.2 m, aligning with the findings of Price et al. (2000). It is important to note that the LDI (Fig. 4e) may underestimate the potential for lateral spread because the CPT was halted at a depth of 15 m, whereas analysis using the SPT indicates that the subsoil remains liquefiable at a depth of 18 m. The values of (N 1 ) 60cs acquired after the ground reinforcement and reported by Rollins et al. (2012) were used to repeat the evaluation of the liquefaction potential taking into account the variation in resistance to penetration of the subsoil. In this case, the LPI drops to 0 and, as a consequence of the absence of liquefiable layers, the D H value obviously become 0.