Particle Shape and Stiffness

dc.contributor.advisor Santamarina, J. Carlos
dc.contributor.author Dodds, Jake Steven
dc.contributor.committeeMember Glenn Rix and Paul W. Mayne
dc.contributor.department Civil and Environmental Engineering
dc.date.accessioned 2006-03-06T20:41:01Z
dc.date.available 2006-03-06T20:41:01Z
dc.date.issued 2004-01-06
dc.description.abstract Particle shape is evaluated on three scales corresponding to form, roundness and roughness. Shape at each of these scales uniquely influences material behavior. The shape of sand grains is largely formed as magma cools. Subsequent cleavage and abrasion change the roundness and roughness of particles. Published results indicate that particle shape influences several aspects of granular systems behavior including stiffness, strength, the evolution of strength anisotropy, dilation, and the development of strain localization. The crushing of granite creates a particulate material with a unique angular shape. A wide range of experimental studies implemented as part of this research permit assembling a unique database of material parameters and comparing the behavior of several crushed and natural sands. In general, the low roundness of crushed sands leads to higher maximum void ratios, lower small strain stiffnesses, and higher critical state friction angles than more rounded natural sands. It also impacts mortar strength and workability. Previous studies have emphasized size-controlled segregation. New experimental results show that differences in particle shape can also lead to segregation in a binary granular material. Round or spherical particles are more mobile than angular or flat particles. Then, the greater motion of round or spherical particles in a binary mixture subjected to horizontal or vertical vibration results in their segregation from their angular or flat neighbors. Particle shape may change significantly with stress in the case of soft particles. Therefore, the presence of shape-deformable particles decreases the stiffness of binary rigid-soft particle mixtures. However, macro-scale measurements with rigid-soft mixtures show higher stiffness than would be expected by volume averaging techniques. A subsequent microscale study shows the formation of backbone chains made of the rigid particles, partially supported by the soft particles which prevent the buckling of the load-carrying chains.
dc.description.degree M.S.
dc.format.extent 2854690 bytes
dc.format.mimetype application/pdf
dc.identifier.uri http://hdl.handle.net/1853/8063
dc.language.iso en_US en
dc.publisher Georgia Institute of Technology en
dc.subject Crushed sands en
dc.subject Sand rubber mixtures
dc.subject Particle shape
dc.title Particle Shape and Stiffness en
dc.type Text
dc.type.genre Thesis
dspace.entity.type Publication
local.contributor.advisor Santamarina, J. Carlos
local.contributor.corporatename School of Civil and Environmental Engineering
local.contributor.corporatename College of Engineering
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