Effects of stress anisotropy on dynamic properties of soils

This study investigates the effects of stress anisotropy on the dynamic properties of soils, with significant implications for the seismic response of structures. Site response analyses conducted for a Class D site in Adapazarı, Türkiye, where severe structural damage occurred during the 1999 Kocaeli earthquake, using global models for soil dynamic properties, failed to provide the necessary amplification to explain the observed damage. In contrast, analyses utilizing a model calibrated to the local soil’s dynamic properties, determined through Cyclic Direct Simple Shear tests with K 0 consolidation, produced the expected amplification. This research emphasizes stress anisotropy as a critical factor influencing soil dynamic properties, demonstrating variations of up to 35%. By employing novel Resonant Column equipment alongside a comprehensive literature database, we propose a model that accurately reflects local soil behavior, integrating small-strain field data with large-strain laboratory results. This model effectively captures the impacts of stress anisotropy on both maximum shear modulus and damping ratio, providing essential empirical relationships for site-response analysis. The findings underscore the risks of relying solely on global models for soil dynamic properties in Class D sites and advocate for locally calibrated relationships that consider specific stress conditions to improve the reliability of seismic assessments.