Estimation of Drained Shear Strength of Granular Soil from Shear Wave Velocity and Confining Stress

Building upon a previously reported hypothesis suggesting a unique linear relationship between the small strain shear modulus and major principal effective stress at failure, this paper proposes a new empirical equation to estimate the drained shear strength from the measured shear wave velocity. A series of drained triaxial tests on clean sands and natural granular soils are performed to measure the shear strength of granular soils. Shear wave velocities are measured using bender elements installed at the top and bottom caps. Although a correlation between maximum shear modulus calculated from the shear wave velocity and effective stress at failure is observed, it is shown that the correlation can be further improved by including the confining stress. A unique relationship between maximum shear modulus, effective stress at failure, and confining stress is shown to exist for all granular soils tested. The predicted secant friction angles from the proposed empirical relationship exhibit good agreement with the measured values. The applicability of the equation is further validated through measured data on silty sand from a published study. Again, very favorable matches with the measured secant friction angles highlight the wide applicability of the proposed empirical relationship. A possible application of the proposed correlation is calculation of the shear strength from the shear wave velocity profile for strength correction in a seismic analysis. (C) 2018 American Society of Civil Engineers.