Vahid Gorbanpoor, - Civil Engineering Faculty, Sahand University of Technology, SUT, Tabriz, Iran
Mehrdad Emami Tabtizi - Civil Engineering Faculty, Sahand University of Technology, SUT, Tabriz, Iran

Determining the mechanical behavior of granular materials has always been of interest. In the meantime, it is necessary to pay attention to the parameters affecting the mechanical behavior and apply them in the constitutive models. Shape of grains is one of the effective parameters. This property affects the fracture strength, compressibility, maximum friction angle and the distribution of contact stresses. So far, laboratory studies on the effect of shape on the behavior of granular materials have focused mostly on comparing the results of angular and rounded grains. Due to the distribution of different shapes in natural grains, experimental studies of the effect of sphericity index are of great importance. On the other hand, it is necessary to investigate the grain shape on the compression model parameters comprehensively. Therefore, based on the energy conservation equation and the use of statistical Weibull and fractal theory, the compressibility model of granular materials under uniaxial loading conditions is obtained. Then, in order to evaluate the analytical model, uniaxial loading tests are performed on four different shapes of grains of the same size under the same conditions. The results show that the proposed compressibility model can consider the effect of the grains shape with acceptable accuracy.

Constitutive Model, Compressibility, Granular, Fractal theory.