Elastic-Plastic Constitutive Model for Unsaturated Intact Loess

The remarkable hydro-sensitivity and structural characteristics of collapsible loess significantly influence its mechanical behavior. This paper, building upon the modified Cambridge model, presents a simplified yet practical elastoplastic constitutive model designed for accurately characterizing the mechanical properties of unsaturated intact loess. The model employs deviatoric and mean stresses as stress variables, and saturation degree as the moisture variable. It leverages the shear strength parameters of unsaturated intact loess to define the critical state surface. By incorporating structural strength into the equation of the elliptical yield surface, an initial yield surface equation is established. This initial yield surface determines the starting point for calculating elastoplastic deformations of samples with varying saturation degrees under stress. The proposed model comprises eight parameters, each with a clear physical interpretation, and these parameters can be readily determined from conventional triaxial tests conducted on specimens with different initial saturation degrees. Through comparison with the stress-strain responses of unsaturated intact loess from various regions, the model's applicability in describing their stress-strain relationships has been validated. The findings of this research are expected to substantially enhance the predictive and preventative capabilities for geotechnical engineering hazards in loess regions, such as foundation settlement and slope stability. Ultimately, this work aims to provide theoretical support for the safe and stable development and construction of infrastructure in loess areas.