Influence of soil aging on SPT-Vs correlation and seismic site classification

• Published in: Engineering geology Vol. 272; p. 105653
• Main Authors: Rahimi, Salman, Wood, Clinton M., Wotherspoon, Liam M.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.07.2020
• Subjects: N SPT-Vs correlation; Seismic site classification; Shear wave velocity; Soil aging; Standard penetration test; Standard penetration test; Soil aging; N SPT-Vs correlation; Seismic site classification; Shear wave velocity
• ISSN: 0013-7952; 1872-6917
• DOI: 10.1016/j.enggeo.2020.105653

This study examines the influence of soil aging on Standard Penetration Test (SPT) N-Vs correlations, and seismic site classification. Energy-corrected SPT-Vs correlations are developed for two regions where subsurface layering consists of soil deposits with very young geotechnical ages according to the last critical soil disturbance that occurred in the study areas. It is observed that the uncorrected correlations of the current study fall into the lower bound of the uncorrected SPT-Vs correlations existing in the literature due to soil aging effects. To better illustrate the effects of soil aging on SPT-Vs correlations, the uncorrected correlations from the literature and this study are divided into two age categories of Holocene and Pleistocene according to their geological age. Using the two age categories, the boundaries proposed in the NEHRP for different seismic site classes are divided into three zones according to their uncertainty level regarding seismic site classification. The results clearly indicate the need to consider the age of soil deposits for seismic site classification when using the SPT method to avoid incorrect seismic site classification. Additionally, it is found that the use of raw (uncorrected) SPT N values can lead to incorrect seismic site classification, with either conservative or unconservative results depending on the Energy Transfer Ratio (ETR) of the SPT hammer used for the seismic site class determination. •Two new age categories of Holocene and Pleistocene are defined for the uncorrected SPTVs correlations for sandy soils.•Energy-corrected SPT-Vs correlation should be used to avoid inconsistency between different studies caused by hammer ETR.•In the SPT method, the use of uncorrected SPT N values can lead to incorrect seismic site classification.•The age of soil needs to be considered for seismic site classification when using the SPT method.