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Although Toyoura sand has been widely used as a standard material for physical model tests (particularly centrifuge model tests), its path-dependent stiffness degradation curves are rarely reported in the literature. This leads to difficulties in back-analyzing and understanding the physical tests involving significant changes in the direction of stress paths (such as unloading problems). In this study, path-dependent stiffness degradation curves of medium-dense Toyoura sand were determined by carrying out a series of stress-path triaxial tests, with local strain measurements. In the triaxial tests, four typical recent stress histories (changes of path direction = 0, 90, –90, and 180°) were simulated. The measured small strain stiffnesses of Toyoura sand were then used to calibrate an advanced hypoplastic model that accounts for path-dependent soil stiffness at small strains. To justify the validity of the calibrated hypoplastic …