Influence of particle shape and size on the dynamic soil properties

Abstract

Shear modulus and damping ratio which are important parameters in any dynamic analysis of soil are related to the frictional behavior at inter particle contacts and rearrangement of grains. The strength loss of granular soil when subjected to cyclic loading is affected by particle size, shape and its distribution. Soil structure also termed as fabric which encompasses grains/particle distribution, particle orientation and arrangement, the voids and the fluid present in between the voids, continually changes during cyclic loading. Such changes are imperative of mechanisms that result in liquefaction of saturated sands and compaction of dry sands. Unlike, experimental and analytical testing methods, numerical methods are equipped to provide insight into these underlying mechanisms. To understand the interactions between particles that influence the dynamic behavior of soil, modeling of cyclic triaxial test was conducted using 3D DEM for different particle shapes and sizes. Before the testing, validation of the generated soil sample is conducted by checking the pressure dependent behavior and dilative response of the sample. Contact normals and contact forces were also used to validate the sample at different stages. From the cyclic testing, normalized shear modulus curves, contact normal and force distributions were calculated. It was observed that the rounded particles had more shear stiffness compared to other shapes. This behavior was not evident when the shear modulus was normalized and the spherical particles had the highest modulus. The effect of particle shape was verified with the change in the coefficient of uniformity (Cu) with shear modulus and it is observed that shear modulus decrease with an increase of Cu. Micromechanical expression for the same was also been discussed.

Influence of Particle Size Distribution and Moisture Content Variability on the Characterization of Soils in Ipinsa Area, Akure, Southwestern Nigeria

“…Produced curves from the other samples also depict a poor grading of its particles as majority possesses a wide gap between their clay and silt fractions. On the other hand, conducted studies on samples with different Uniformity Coefficient (CU) but with no reference to general level of gradation (Manne and Devarakonda, 2016;Eze et al, 2017). Sample S1 which is a poorly graded soil has a curve which stands between the convex curve of S19D and concave curve of S7 (Figure 4b).…”

“…However, some earlier studies had initially proposed that most of the qualitative physical properties of soil cannot be related to particle size distribution (Dapples, 1959;Gidigasu, 1976). Hitherto, qualitative physical properties of natural soils were given as volume change, strength under tension, plasticity, porosity, permeability, size of pore openings, water retention and base exchange capacity (Lee, 1992;Radjai et al, 1998;Manne and Devarakonda, 2016). Yet, generally, it was believed that some class of soils, most especially coarse-grained and cohesionless soils, have their grain size distributions indicative of most physical properties.…”

Experimental micro–macromechanics: particle shape effect on the biaxial shear response of particulate systems

“…On the other hand, several numerical studies using the discrete element method (DEM) have been carried out to investigate the effects of particle shape (e.g., Nguyen et al, 2020). DEM models of non-spherical/circular particles often employ elliptic particles or bonded agglomerates (e.g., Manne et al, 2015;Kodicherla et al, 2020). Elongated shapes were modeled by various techniques, such as bonding two or more spherical or circular particles together (Manne et al, 2015).…”

“…DEM models of non-spherical/circular particles often employ elliptic particles or bonded agglomerates (e.g., Manne et al, 2015;Kodicherla et al, 2020). Elongated shapes were modeled by various techniques, such as bonding two or more spherical or circular particles together (Manne et al, 2015). Angular particles have also been used to consider realistic shapes of soil grains (Mirghasemi et al, 1997;Azéma et al, 2007;Zhao and Zhou, 2017;Binaree et al, 2019;Wu et al, 2021).…”