A strain work constitutive model for structured soils

The mechanical behavior of structured soils is influenced by both inter-particle bonding and fabric arrangements. Existing constitutive models primarily account for soil structure through fabric arrangements. In this study, we first present experimental investigations on intact loess samples, including isotropic compression (IC), conventional consolidation undrained (CU), and consolidation drained (CD) triaxial tests, which reveal the complex structural properties of the soil. Next, we employ the work done by strain energy to comprehensively account for soil structure, incorporating both inter-particle bonding and fabric arrangements. Subsequently, a new strain work constitutive model for structured soils is presented within the critical state framework. Specifically, a linear decreasing function between strain power and mean effective stress is introduced to capture structural degradation, and a new hardening rule is derived from the relationship between strain work and mean effective stress. Compared to traditional structured soil models, the proposed model offers clear physical meaning, and its parameters are easily obtainable. The model's simulation results are validated against experimental data, demonstrating its ability to capture key mechanical and deformation characteristics, such as strain softening under CU conditions and strain hardening under CD conditions. Finally, we compare our model with the structured cam clay (SCC) model, and the results show that our model provides a better fit to the experimental data, further confirming its accuracy and effectiveness.