Particle Shape Effects on Packing Density, Stiffness, and Strength: Natural and Crushed Sands

Abstract

The size and shape of soil particles reflect the formation history of the grains. In turn, the macroscale behavior of the soil mass results from particle level interactions which are affected by particle shape. Sphericity, roundness, and smoothness characterize different scales associated with particle shape. New experimental data and results from published studies are gathered into two databases to explore the effects of particle shape on packing density and on the small-to-large strain mechanical properties of sandy soils. In agreement with previous studies, these data confirm that increased angularity or eccentricity produces an increase in e max and e min . Furthermore, the data show that increasing particle irregularity causes a decrease in stiffness yet heightened sensitivity to the state of stress; an increase in compressibility under zero-lateral strain loading; an increase in the critical state friction angle cs ; and an increase in the intercept ⌫ of the critical state line ͑there is a weak effect on the slope ͒. Therefore, particle shape emerges as a significant soil index property that needs to be properly characterized and documented, particularly in clean sands and gravels. The systematic assessment of particle shape will lead to a better understanding of sand behavior.

Breakage of an artificial crushable material under loading

“…At the same time, the decrease of d M with increasing η max is more pronounced for larger values of U i ; this likely to be due to the fact that, at the same value of d 50i , well graded samples contain particles of larger size with a higher probability of containing defect or flaws (e.g. [6]). Figure 13 shows the observed variation of β and d M as a function of the maximum mean effective stress p max attained during one-dimensional compression for the eight tested cumulative initial grain size distribution (see Fig.…”

Influence of Particle Size on the Friction and Interfacial Shear Strength of Sands of Similar Morphology

“…P is perimeter of any horizontal projected section of the particle at rest Janoo [27] A is the area of the profile of the particle projection Sphericity (S) 2 ffiffiffiffi pA p P A and P are same as above Sympatec [30] Regularity (q) ðRþSÞ 2 S = sphericity, R = roundness Cho et al [8] Roughness (R p ) P Pc P = perimeter of particle Janoo [27] P c = convex hull perimeter of particle Pictorial representation of notation P e P c P A supporting frame connected to vertical rod to create an obstruction free foreground to the shear box for capturing images and videos (refer part 7 in Fig. 3).…”

“…The stress-strain response and volume change behavior of sands in shear and interface shear are mainly influenced by the normal stress, method of testing and testing materials [1][2][3][4][5][6], morphological characteristics of sand [7][8][9][10][11][12] and surface roughness of the geosynthetic material at the interface [13][14][15][16][17][18]. Morphological characteristics of sand grains reflect the formation process, transportation process and material composition.…”

“…Several studies are available in literature that correlate the morphological characteristics of sand grains to the shear strength. Through systematic analysis of microphotographs of sand grains and oedometer tests, Cho et al [8] observed that the increase in angularity of grains leads to increase in constant volume critical state friction angle and recommended that particle shape should be characterized and should be included in the classifications, especially for gravels and sands. Lim et al [19] showed that particle shape and size have significant influence on the engineering properties of sands.…”

Systematic Approach for Large-Scale, Rapid, Dilapidation Surveys of Historic Masonry Buildings

“…Index images are commonly employed within Civil Engineering as well as related fields to provide a visual standard for guidance, e.g. Cho et al (2006), Grünthal et al (1998).…”