A Double-Yield-Surface Elastoplastic Constitutive Model for Cemented Sand and Gravel Dam Materials

Cemented sand and gravel (CSG) exhibits distinct shear and volumetric deformation responses. This study assesses a double-yield-surface incremental formulation and recalibrates its axial and volumetric response relations using coordinates digitized from the available triaxial plots. Three binder contents, 20, 60, and 100 kg/m3, are examined at confining pressures of 300–1200 kPa. Stress-induced yield differentials, plastic multipliers, and the coefficients used for triaxial path matching are distinguished. Mixture-specific parameters and yield-contour shape ratios are reported, and the necessary axial condition Et ≤ E is satisfied over the investigated ascending branches. The pointwise calibration root-mean-square residuals range from 31 to 131 kPa in deviatoric stress and from 0.021 to 0.179 percentage points in volumetric strain. These are in-sample fitting statistics, not independent prediction errors or estimates of specimen-to-specimen variability. Published test methods are briefly summarized, while specimen-level records and replicate variability associated with the digitized curves remain uncertain. The volumetric-hardening relation requires additional source-state information for independent reconstruction. Accordingly, the findings support an assessment of graphical calibration within the reported stress and strain ranges, rather than independent validation or completed numerical model implementation.