Effective stress hyperbolic stress-strain parameters for clay

This paper presents a procedure for estimating the effective stress hyperbolic stress-strain parameters for normally consolidated clays from the results of consolidation and direct shear tests. The procedure for calculating Young's modulus and the modulus number includes: (1) estimating the failure ratio from the shear stress-horizontal displacement curve obtained from a direct shear test; (2) using a tangent modulus at the end of each normally consolidated load increment in the consolidation test and the void ratio at the beginning of each load increment to calculate Young's modulus; and (3) multiplying the resulting modulus number by 1.9 to obtain a reasonable estimate of the isotropically consolidated-drained triaxial (CID) modulus number. The modulus exponent was approximately unity for both the consolidation and CID triaxial tests. A procedure for estimating the bulk modulus number, the bulk modulus exponent, and the unload-reload modulus number is also presented.