Civil Engineering ETDs

Publication Date

Spring 1-20-2021

Abstract

This research reports on confined Brazilian strength tests and concurrent permeability testing on sandstone. The majority of the tests measured permeability during loading to failure in the confined extension region. Additional testing includes unloading and reloading cycles to detect the development of microcracks and the dependence of permeability on mixed stress conditions. Further testing characterizes fracture networks by observing porosity changes due to microcrack interactions before peak load. All tests involve 5 cm diameter disk-shaped, jacketed samples that are subjected to confining stresses while they are diametrically loaded. Specially designed end caps allow for gas flow measurements. The test configuration allows a range of stresses to be applied, with the confining pressure as σ2, the intermediate principal stress. σ2 is shown to have a significant impact on failure conditions in the confined extension region. Permeability is shown to increase well before the peak load is reached, indicative of a connected microcrack network that develops during loading. Numerical modeling comparisons predict similar failure conditions to experimental tests and examine variations in observed fracture patterns.

Keywords

sandstone, permeability, microcracks, fracture, numerical, modeling

Sponsors

Los Alamos National Laboratory

Document Type

Thesis

Language

English

Degree Name

Civil Engineering

Level of Degree

Masters

Department Name

Civil Engineering

First Committee Member (Chair)

John Stormont

Second Committee Member

Mahmoud Reda Taha

Third Committee Member

Esteban Rougier

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