In this study, the small-strain shear modulus of a calcareous sand was investigated by conducting bender element tests on both horizontal and vertical planes. The effects of sample preparation method, stress path and stress history on the developing of void ratio, the parameters in the modified Hardin Equation, and the stiffness anisotropy were examined. The test results show that the moist tamping samples have the least void ratio variation among the five samples. The void ratio recovery in effective horizontal stress [Formula: see text] = 100 kPa tests is higher than that in the effective vertical stress [Formula: see text] = 100 kPa tests. The samples prepared in the dry state have lower stiffness than those prepared in the moisture state, which is not influenced by the anisotropic stress state. The stiffness anisotropy induced by the sample preparation method is significant under anisotropic consolidation. In [Formula: see text] = 100 kPa tests, the stiffness ratios at the end of the unloading stage are lower than the initial values at the loading stage, which is not found in the [Formula: see text] = 100 kPa tests, meaning that the stress history and stress path could affect the stiffness anisotropy and eliminate the impact of fabric anisotropy. 

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Small-strain shear modulus of calcareous sand under anisotropic consolidation

Small-strain shear modulus (G0) is a fundamental property required in dynamic analyses. For sandy soils, G0 may be affected strongly by particle characteristics such as uniformity coefficient (Cu), mean particle size (d50), fines content (FC), and particle shape. Based on an extensive experimental study of the mechanical behavior of coral sands, this paper proposes a new formula for predicting G0 for sandy soils with various Cu, d50, FC, and particle shapes. A notable feature of the new formula is the use of the extreme void ratios (maximum void ratio emax and minimum void ratio emin) as the indexes, which were shown to be able to account for the effects of the various factors in a simple yet collective manner. Power-law correlations were established between the minimum small-strain shear modulus G0min and emax as well as between the maximum small-strain shear modulus G0max and emin. The wide applicability of this formula was validated further using extensive data from the literature from resonant column, bender element, and torsional shear tests on siliceous, calcareous, and coral sandy soils. 

Tao Xu

Papers

Effect of non-plastic fines on the anisotropic small strain stiffness of a calcareous sand