Estimation and Calibration of Hardening Soil Model Parameters for Cohesive Soil Using PLAXIS: A Case Study of Darbandikhan Dam

This study mainly focuses on identifying and calibrating the Hardening Soil Model HSM parameters for reconstituted soil samples representing the clay core of Darbandikhan Dam. Data from previous investigations and laboratory tests were coupled with numerical modeling to estimate the key parameters, such as stiffness moduli, stress dependency power of stiffness, and shear strength parameters. The reference secant modulus E50 was derived from replicated consolidated undrained triaxial tests at different confining pressures using PLAXIS, with a calibrated value of E_50^ref= 3100 kN/m². Oedometer stiffness Eoed was estimated from one-dimensional consolidation tests under different density and moisture content conditions, yielding a reference modulus of 3320 kN/m². Key findings indicate significant variability in soil stiffness and stress dependency, with a stiffness exponent (m) ranging from 0.66 to 0.80, influenced strongly by initial density and moisture content. The friction angle (φ) was calibrated to 25°, aligning closely with historical data. Finally, the simulated results based on the parameters numerically calibrated against undrained triaxial tests using PLAXIS finite element software showed strong agreement with the laboratory results.