Date of Graduation

12-2018

Document Type

Thesis

Degree Name

Master of Science in Civil Engineering (MSCE)

Degree Level

Graduate

Department

Civil Engineering

Advisor/Mentor

Barry, Michelle L.

Committee Member

Coffman, Richard A.

Second Committee Member

Hall, Kevin D.

Keywords

Additive Manufacturing; Geotechnical Engineering; Granular Materials; Particle Shape; Size Effects; Triaxial Testing

Abstract

Triaxial testing is one of the fundamental laboratory tests used in geotechnical engineering to determine strength parameters, such as shear strength and friction angle. Investigating the minimum representative elementary volume (REV) can verify the independence of size effects on strength parameters and ensure that the scaled laboratory tests results are consistent, repeatable, and representative of field conditions. Although, REV has been studied for many applications, there is disagreement within geotechnical engineering of a minimum particle diameter to specimen diameter to minimize the size effects related to the REV in consolidated drained (CD) triaxial tests. This research study compared the strength results of three different specimen diameter sizes to understand the size effects and to investigate the influence of particle shape by using 3D printed spheres and scaled Ottawa sand. 3D printed particles allows different influencing variables on strength parameters such as shape, size, gradation, and surface roughness to be controlled within the granular soil. By isolating a factor, such as shape in this case, the response of the soil can be more clearly understood and a representative REV can be determined. The scaled Ottawa sand and spheres had a greater increase in variability as the diameter decreases, implying that the REV was not met for the 7.11 cm specimen diameter. It is recommended that a minimum specimen diameter should be at least nine times greater than the maximum particle diameter for spheres and subrounded particles in consolidated drained triaxial testing in order to minimize size effects.

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