Numerical simulations and calibration of hypoplasticity constitutive parameters for Chicago clays are presented based on laboratory tests conducted on high-quality block samples and field tests from excavations located in the Chicago, Illinois area. The parameters for the hypoplasticity model enhanced with the intergranular strain concept are calibrated from the results of index tests, oedometer tests, and K0-consolidated undrained triaxial compression and extension tests. Drained stress probes conducted in a triaxial cell after three different preshearing stress paths were used to compare the numerical results with the triaxial test results. One path was applied to study the clay stress-strain behavior at in situ conditions and the remaining two to isolate the effects of recent stress history. The results are shown in terms of the secant shear and bulk stiffness, shear and volumetric stress-strain responses at small and large strains, and stress path reversals.