Determination of Key Parameters for the Small-Strain Hardening Soil Model and Engineering Validation: A Case Study of Typical Soils in Taiyuan, China

The Hardening Soil model with small-strain stiffness (HSS) is widely adopted in the numerical analysis of deep excavations and tunneling due to its ability to capture non-linear deformation and stress-history dependency. However, the determination of its key stiffness parameters remains regionally uneven, limiting its application in distinct geological contexts. To address this gap, this study systematically analyzes the physical significance and experimental determination methods of key HSS parameters. Based on comprehensive laboratory testing, including standard consolidation, consolidated undrained triaxial, empirical correlations and quantitative normalized stiffness ratios among the three reference stiffness parameters (Eoedref, E50ref, Eurref) and the small-strain shear modulus (G0ref) were established for typical soil layers in Taiyuan. Additionally, recommended values for the stress dependency exponent m were determined. The derived parameter ratios were implemented in a finite element analysis of a representative deep excavation project, where the predicted wall deflections and ground settlements showed good agreement with field monitoring data. The results demonstrate that the calibrated regional parameter system provides reliable deformation prediction and improves the transparency and consistency of HSS parameter selection. These findings not only provide a reference for HSS parameter selection in the Taiyuan region but also offer a highly applicable framework for establishing similar parameter systems in other geological contexts.