Masahide Otsubo

TL;DR: Empirical expressions relating Δtcrit to m, Kmax, and CN,max are presented; while strictly only valid within the range of simulation scenarios considered here, these can inform DEM analysts selecting appropriate ΔtCrit values.

TL;DR: The relationship between soil stiffness and isotropic confining pressure can be described using a power function with exponent (b), that is, G0 = A (p′/pr)b, where A is a constant and pr is an arbitrary reference pressure as mentioned in this paper.

TL;DR: In this paper, the effect of surface roughness on the shear wave velocity and the small-strain stiffness of soils using both laboratory shear plate dynamic tests and discrete element method (DEM) analyses was assessed.

Abstract: Discrete-element method (DEM) simulations of planar wave propagation are used to examine the effect of particle surface roughness on the stiffness and dynamic response of granular materials. A new contact model that considers particle surface roughness is implemented in the DEM simulations. Face-centred cubic lattice packings and random configurations are used; uniform spheres are considered in both cases to isolate fabric and contact model effects from inertia effects. For the range of values considered here surface roughness caused a significant reduction in stiffness, particularly at lower confining stresses. The simulations confirm that surface roughness effects can at least partially explain the value of the exponent in the relationship between stiffness and mean confining stress for an assembly of spherical particles. Frequency domain analyses showed that the maximum frequency transmitted through the sample is reduced when surface roughness is considered. The assumption of homogeneity of stress and ...

TL;DR: In this article, the authors carried out a reconnaissance of Mexico City, and some locations in the states of Puebla and Morelos, to identify the affected areas and the extent of damage.