Yasser Abdelhamid

Pore-Scale Modeling of Fine-Particle Migration in Granular Filters

AbstractFine-particle migration and associated internal erosion are major concerns for dam safety. Granular filters are used to prevent fine-particle migration, and several empirical models have been introduced for the design of these filters. Few computational techniques have tracked particle transport through the filters. This paper presents a three-dimensional transient fully coupled pore-scale model used to study the mechanism of fine-particle migration in granular filters. A pore-scale idealization of the fluid was achieved by using the lattice Boltzmann method, and the solid phase was modeled at a microscale using a discrete element method. The fluid forces applied on the particles were calculated on the basis of the momentum exchange between the fluid and particles. The proposed numerical technique was used to model the migration of base-soil particles through granular filters of different particle sizes. Results of conducted simulations provided the erosion percentages and flow rates during the si...

Multiscale Modeling of Flood-Induced Scour in a Particle Bed

A three-dimensional transient fully coupled fluid-particle model is presented to simulate fluid flow-induced scour of a particle bed. The interaction of the liquid and solid phases is the key mechanism related to flood-induced failures of geotechnical systems. In this model, the mix of soil particles and water is idealized as two interpenetrating phases, each of which is modeled at a different scale. The fluid phase is idealized as a continuum using Eulerian formulation of averaged NavierStokes equations that account for the presence of the solid particles and solved using the finite element method. The particles are modeled at a microscale using the discrete element method. Computational simulations are conducted to investigate the response of a particle bed to Poiseuille flow conditions. The simulations provided information at the microscale level for the solid phase and the macroscale level for the fluid phase.

Some Aspects of the Impact of Multidirectional Shaking on Liquefaction of Level and Sloping Granular Deposits

AbstractA very limited number of computational studies have been presented for the analysis of the response of saturated granular soils to multidirectional shaking despite it being the realistic mode of loading that resembles an actual earthquake. Herein, this paper examines the capabilities of a recently developed, coupled lattice Boltzmann method (LBM)–discrete element method (DEM) of modeling level and gently sloped soil deposits when subjected to bidirectional shaking. The results of conducted simulations show that bidirectional shaking may increase surface settlement of level deposits by about 30% over unilateral shaking. The depth along the deposit that experiences excess pore pressure ratio close to unity increases as a result of bidirectional shaking compared to unilateral shaking. Bidirectional shaking also increases the magnitude of lateral spreading and associated shear strains in sloping deposits. Other aspects of the response include capturing soil dilative behavior and associated temporary i...

Multiscale Modeling of Fine Particles Migration in Granular Filters

We present early results of a fully coupled transient three-dimensional model employed to study fundamentals of fine particles migration in granular filters. Filtration process and internal erosion are a particle level phenomenon. A numerical model that is capable of tracking the migration of the base soil particles through the filter pores at a microscale is therefore needed. The discrete element method is used to model the granular material. The pore fluid is modeled at a mesoscale and solved using the lattice Boltzmann method. The proposed approach is used to model the migration of base soil particles through a granular filter. Results of conducted simulation provide the erosion percentage and flow rate during the simulation.

Liquefaction of Granular Soils at the Microscale

In this study, we introduce results of a novel coupled pore-scale model of pore-fluid interacting with discrete particles for soil liquefaction. A mircoscale idealization of the solid phase is achieved using the discrete element method (DEM) while the fluid phase is modeled at a mesoscale using the lattice Boltzmann method (LBM). The fluid forces applied on the particles are calculated based on the momentum exchange between the fluid and particles. The proposed approach is used to model liquefaction of a saturated granular soil deposit subjected to seismic excitations. Results of conducted simulations suggest that liquefaction is due to reduction in void space during shaking that leads to buildup in pore-fluid pressure.

Multiscale Modeling of Soil-Fluid-Structure Interaction

We present early results of a fully coupled transient two-dimensional model employed to study fundamentals of flood-induced failure of geotechnical systems while taking into consideration the effect of soil-fluid-structure interaction. The interaction of the liquid and solid phases is the key mechanism related to flood- induced failures of geotechnical systems. The solid phase is idealized at a particle scale by using the discrete element method. The fluid phase is modeled at a mesoscale level and solved using the lattice Boltzmann method. The structure is modeled as a rigid wall that interacts with the particles and fluid. The proposed approach is used to model a sheet pile wall subjected to an increasing water pressure. The velocity of the particles and fluid are monitored during the simulation. The simulation provides the fluid velocity in the pores. The classical seepage total head contours are retrieved from the numerical simulation. As the hydraulic head difference increases, the upstream bed surface settles and the downstream bed surface heaves.