Multiple shear spring model with modified masing rules for cyclic degradation analysis

This paper presents a significant advancement in geotechnical modeling through an enhanced Multiple Shear Spring Model (MSSM) for simulating cyclic soil behavior. The innovative approach combines a sig4 backbone curve formulation with modified Masing rules and a novel degradation framework, addressing critical limitations in existing models. The MSSM's distinctive feature lies in its ability to decompose three-dimensional strains into distributed one-dimensional components, enabling accurate representation of complex soil responses under cyclic loading. Two key innovations are introduced: (1) an adaptive homothetic ratio for the modified Masing criterion, significantly improving hysteretic damping predictions at medium to large strain levels, and (2) a novel degradation index formulation that captures the evolution of soil stiffness during cyclic loading. The integration of these enhancements within the MSSM framework demonstrates remarkable improvements in predicting stress-strain hysteresis loops, with degradation characteristics accurately captured across multiple loading cycles. Validation against experimental data from strain-controlled triaxial simple shear tests on kaolinite clay demonstrates the model's superior performance in predicting both stress-strain relationships and damping characteristics. The enhanced MSSM framework, particularly through its innovative degradation index formulation, provides a robust tool for advanced seismic response analysis and geotechnical design applications. The model's ability to accurately simulate both initial and degraded stress-strain behavior represents a significant contribution to cyclic soil modeling, offering improved reliability in predicting soil response under various loading conditions.