Abstract
Size limitations of geotechnical testing equipment often require that samples of coarse granular materials have to be scaled in order to be tested in the laboratory. Scaling implies a convenient modification of the particle size distribution (PSD) to reduce particle sizes. However, it is well known that particle size and shape may be correlated in nature, due to geological factors (as an example). By means of two-dimensional contact dynamics simulations, we analyzed the effect of altering the size span on the shear strength of granular materials when particle size and shape are correlated. Two different systems were considered: one made of only circular particles, and the second made of size-shape correlated particles. By varying systematically the size span we observed that the resulting alteration of material strength is not due to the change in particle sizes. It results instead from the variation of the particle shapes induced by the modification of the PSD, when particle size and particle shape are correlated. This finding suggests that particle shape distribution is a higher order factor than PSD for the shear strength of granular materials. It also highlights the importance of particle shape quantification in soil classification and the case for its consideration in activities such as sampling, subsampling, and scaling of coarse materials for geotechnical testing
Highlights
1 Introduction shear strength may increase or decline depending on the Correlation of particle size and particle shape can occur in nature due to geological factors [1] and it has been reported in the literature [2, 3]
The plausible origin for such a discrepancy is that the sampling and the scaling employed for laboratory testing, in the case of coarse granular materials like mine wastes, inadvertently alters the particle shape polydispersity of the sample, limiting its capacity to reproduce the mechanical behavior of the original material [14]
A systematic analysis is presented in this paper, on the effect of particle size and shape on the strength properties of granular material by means of contact dynamics simulations
Summary
The simulations were carried out by means of the contactdynamics (CD) method [15,16,17] implemented in the multipurpose software LMGC90 developed in University of Montpelier. 5, allowing to relate the aspect ratio of a given particle to be related to it’s diameter d by: With this equation larger particles in a sample are the more elongated, and more widely graded samples (more polydisperse in particle sizes) are more polydisperse in particle shapes, in alignment with the situation observed in the mine waste explored in [4]. Vy was set such that the inertial number I was keppt in the order of 5 · 10 4 It is defined by I = (vy/H)hdi ⇢/ 0, where H is the sample height, hdi is the mean particle diameter, and ⇢ is particle density,
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