عنوان مقاله [English]
Geological studies indicate that many tropical regions of the planet, including the southern part of Iran, are covered by calcareous sediments. Despite the high risk of seismicity and strategic position as well as the enormous resources of oil and gas in southern Iran, dynamic behavior of calcareous soils of these regions has not been much considered. Therefore, assessing dynamic
behavior of calcareous soils is a vital step for engineering projects located in these regions. Maximum shear modulus is one of the most important properties of soil deposit used in the dynamic analysis.In this study, shear modulus of Boushehr calcareous sand is investigated in the range of small strains using resonant column tests. Bulk samples of Boushehr sand were collected from the North bank of the Persian Gulf near the Boushehr port. The effects of mean confining pressure and void ratio on the maximum shear modulus of the calcareous sand are investigated. Moreover, for evaluating the effect of stress anisotropy on the small-strain shear modulus of the calcareous sand, resonant column tests were conducted under both isotropic and anisotropic conditions.The experimental results confirm that the increase of the mean confining pressure and decrease of the void ratio increases the maximum shear modulus of the sand, as previously reported for the other sands. Also, the results of resonant column tests indicated that the increase of stress anisotropy leads to the increase of maximum shear modulus. By increasing mean confining pressure, the effect of initial stress anisotropy on the maximum shear modulus increases. Based on the tests results, predictive equation for estimating the maximum shear modulus of calcareous sand is presented in this study. It is demonstrated that the proposed model has great capability for prediction of the experimental shear modulus at small strains, compared with the models recommended for silicate soils. Finally, to capture the influence of stress anisotropy on the maximum shear modulus equation, a relationship is presented as a function of initial shear stress ratio. The relationship presented in this study can be employed to evaluate the maximum shear modulus of Boushehr calcareous sand under both isotropic and anisotropic conditions.