Keywords

Particle packing, compressibility, time dependent behavior, constant rate of strain, pseudo K0-consolidation, shear wave velocity, shear modulus, yielding, critical state, liquefaction.

Abstract

Understanding the mechanical response of granular materials is fundamental to geotechnical engineering design. The presence of fines significantly influences the stress-strain-strength behavior, particularly when the material response is controlled by fines content. In this study, Florida sands were initially characterized by their grain distribution and particle morphology, while natural fines were evaluated according to their plasticity characteristics. Two materials were selected for detailed investigation: clean sands and a sand-fines mixture containing 20% fines, representing the threshold between coarse- and fine-dominated behavior. Constant rate of strain (CRS) consolidation tests were performed in both materials to study compressibility and effect of strain rate. Both materials exhibited isotache behavior with minor deviations in compressibility curves following abrupt changes in strain rate. In addition to the consolidation stage, samples were also subjected to creep and relaxation stages for different void ratios, stress levels, and strain rates. The creep analysis showed that the twenty percent addition of fines was the transitional FC that separates the behavior from coarse to fine dominated. Compressibility under pseudo K0-consolidations was studied using a triaxial apparatus and compared against CRS results. During consolidation, shear wave velocity measurements using bender elements were employed to monitor the evolution of the maximum or small-strain shear modulus (G0), while K0 conditions were assessed by controlling the radial strains. Once a desired in situ conditions were reached, samples were subjected to fully drained creep to minimize rate effects and simulate aging. Subsequent sample shearing under drained and undrained conditions allowed determination of critical state lines in stress space and log(p’)-e space. Liquefaction potential was also studied with empirical methods alongside an evaluation of brittleness. Small strain behavior was explored through axisymmetric stress probing of both materials. The analysis revealed two distinct yield limits for both materials at strain levels smaller than the conventional yield strains.

Completion Date

2025

Semester

Summer

Committee Chair

Arboleda, Luis

Degree

Doctor of Philosophy (Ph.D.)

College

College of Engineering and Computer Science

Department

Civil, Environmental and Construction Engineering

Format

PDF

Identifier

DP0029585

Language

English

Document Type

Thesis

Campus Location

Orlando (Main) Campus

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