عنوان مقاله [English]
Recent studies have revealed that silty sand subjected to cyclic loadings is relatively more prone to liquefaction. Therefore, application of existing frameworks, mostly built upon experimental observation on the liquefaction behavior of clean sand, may lead to unsafe design. Technically, in silty sand, silt grains fill the empty spaces between the larger sand grains, but their contribution in load bearing structures is less than that of sand grain. As a result, the reduction of void ratio associated with the presence of fines does not lead to the, so-called, denser load bearing structure. In this regard, the intergranular void ratio defined, based upon the void ratio of those grains participating in the load carrying structure, is a more reasonable index of the density of the load bearing structure in silty sand. The existing state dependent constitutive models exhibit deficiencies in systematic simulation of the mechanical behavior of clean and silty sands with different fines content in a unified manner. In this paper, it is shown that replacing the general void ratio by the intergranular void ratio in the existing constitutive models leads to a unified framework for prediction of the mechanical behavior of both clean and silty sands. While a significant scatter is observed in the steady state lines of the samples with different fines contents, depicted in terms of global void ratio, it is shown that steady state lines drawn, based on the intergranular void ratio, are located in a narrow range. Simulations obtained from the modified model are compared with the experimental data on clean and silty sands reported by two independent research teams. Experimental data consist of the results of triaxial tests on dense, medium, and loose samples conduced under low and intermediate stress levels. It is shown that the mechanical behavior of samples with different fines content can be predicted using a unique set of parameters.