Comparative Assessment of Mohr-Coulomb and Hardening Soil Models for Deep Excavation Design in Stratified Soils: Insights from Numerical and Field Data

This study presents a comprehensive numerical and experimental investigation into the performance of deep excavation support systems in stratified soil conditions. A real-world case study from the OuedSmar metro station in Algiers serves as the basis for evaluating the predictive capabilities of two widely used soil constitutive models: Mohr-Coulomb (MC) and Hardening Soil (HS). The excavation, supported by a diaphragm wall and multi-level anchoring system, was instrumented with inclinometers to capture high-resolution displacement data throughout construction. Finite element simulations were conducted using PLAXIS 3D, and model outputs were compared against field measurements to assess accuracy. Results indicate that the HS model consistently outperformed the MC model, accurately replicating wall deflection magnitudes, deformation profiles, and boundary conditions with errors below 12%, while the MC model significantly overestimated displacements and failed to capture observed behavior. The findings underscore the limitations of simplified constitutive models for serviceability limit state analysis and demonstrate the necessity of using advanced elastoplastic formulations like the HS model in deep urban excavations. This research contributes to improved model selection and calibration practices for safe, reliable, and cost-efficient geotechnical design.