Award Date

1-1-2001

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Civil and Environmental Engineering

First Committee Member

Moses Karakouzian

Number of Pages

133

Abstract

Portions of the high-level nuclear waste repository in Yucca Mountain will be located in lithophysae-rich tuff formations. Understanding the mechanical properties of the lithophysae-rich tuff, including deformation modulus, deformation ratio and compressive strength, is an important issue for design and the performance of the repository tunnels. These properties are expected to be significantly affected by lithophysal porosity; Two different research directions are implemented in this dissertation. First, uniaxial compression testing is simulated using finite difference technique on models containing circular holes in order to investigate the effect of porosity on deformation parameters. Numerical results are compared with biaxial test results of urethane specimens containing circular tubes to verify the numerical analysis results; Second, an experimental program that consists of uniaxial compression tests on analog models and tuff is conducted. Two different configurations are implemented to model porosity using gypsum plaster as an analog material. In the first configuration analog models containing uniformly and randomly distributed open ended cylindrical tubes are produced. In the second configuration spherical cavities are introduced into the analog models. Both models are tested under uniaxial compression and their deformation moduli and compressive strength are compared with lithophysae-rich tuff specimens that are obtained from outcrops of lithophysal tuff units; Numerical modeling and testing are combined to assess that the deformation modulus of tuff where the porosity has a vital effect on mechanical behavior of the rock. Both numerical analysis and uniaxial testing on analog materials show that in deformation modulus exponentially decrease with increasing porosity. The deformation moduli and compressive strength of gypsum plaster specimens containing open ended cylindrical tubes are slightly lower than those containing spherical cavities due to confinement effects; The deformation moduli and compressive strengths of the tuff specimens fall between the values determined for the plaster specimens with two different porosity configuration. Distribution of data for both analog and tuff specimens is very similar at low porosities. At higher porosities, a greater decrease in deformation modulus is observed in tuff due to larger and nonspherical cavities indicating that shape of the cavities is a factor affecting the modulus.

Keywords

Analogs; Deformation; Deformation; Elastic Modulus; Experimental; Investigation; Lithophysae; Lithophysae-rich; Materials; Numerical; Porosity; Properties; Rich; Strength; Tuff

Controlled Subject

Civil engineering; Materials science

File Format

pdf

File Size

2570.24 KB

Degree Grantor

University of Nevada, Las Vegas

Language

English

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