Date of Award

8-2017

Degree Type

Thesis

Degree Name

Master of Science

Major

Civil Engineering

Major Professor

Khalid Alshibli

Committee Members

Claudia Rawn, Angel Palomino

Abstract

Tensile strength of granular materials under one-dimensional (1D) compression is often examined because granular materials fracture in many applications where the soil mass experience high compression stresses. Through methods such as 1D compression, three-dimensional (3-D) imaging, and discrete element modeling, researchers had determined that the Weibull distribution is a good model to represent the tensile strengths of granular material and the fracturing strength of granular materials is dependent on mineralogy, morphology, grain-size, loading rate, gradation, coordination number, and moisture content. Uniaxial compression experiments were performed on Mason sand particles retained between US sieve #10 (2 mm) and #20 (0.84 mm) and retained by sieve #10 (2 mm) to measure fracture loads, particle diameter in the loading direction (dL), tensile strengths, and fracture modes. Visual mineral inspections of particles provided pre-fracture and post-fracture particle descriptions, particle shape, morphology, and mineralogy, which is classified based on particle color collaborated with x-ray diffraction analysis of particle mineralogy. Synchrotron micro-tomography (SMT) imaging is performed on 14 mason sand particles to examine the effects of fracture modes and internal structure on particle tensile strength. The Weibull distribution model is utilized to examine the characteristic tensile strength, the tensile strength at which 37% of particles had a probability surviving, and correlation between particle size and tensile strength; an in-depth analysis is provided to examine the accuracy of the characteristic tensile strength of the Weibull model to the tensile strength at which 63% of particles fracture. The influences of particle size, mineralogy, shape, morphology, surface texture, fracture mode, and internal structure on the tensile strength of single sand particles are examined. Particles with smaller dL, were platy shaped, subangular, smooth, and had less internal flaws generally fractured at higher tensile strengths; particle mineralogy influenced tensile strength in all factors.

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