Subcritical time-dependent response of Berea sandstone

With the increasing development of underground engineering projects in rock formations, construction and storage activities introduce stress disturbances within the subsurface layers. The response of rocks to these disturbances unfolds over extended periods, sometimes spanning months to years, giving rise to time-dependent deformation. Laboratory- and field-scale observations indicate that such time-dependent behavior can lead to significant changes in material properties, as well as the formation of micro- and macro-cracks within the intact rock. The presence of in-situ pore fluids further complicates the process by promoting the crack growth due to stress corrosion cracking and modifying the stress field during the diffusion process. All of these factors pose additional and unpredictable risks to engineering stability, even before the material reaches its apparent strength limit. In this study, the constitutive model describing poro-visco-elasto-plastic behavior of a fluid-saturated rock is adopted. Inelastic time-dependent deformation of Berea sandstone is evaluated in the compression tests, with a stepwise loading method applied. To assess time-dependent behavior, axial and lateral strains are measured during uniaxial compression, as well as triaxial drained and undrained compression tests. Both shear and bulk viscosity are calculated to track changes across different loading stages. Additionally, acoustic emission is monitored throughout each experiment to observe the evolution of microcracks as the load increases. The evolution of permeability (closely related to deformation of the pore space) is also recorded at different stages of loading. This set of interrelated attributes offers a comprehensive and reliable characterization of the fundamental principles governing time-dependent deformation in rocks under different boundary conditions. This study indicates that creep exhibits a linear trend at low-pressure stages, while, when deviatoric stress reaches 80% of the ultimate load-bearing capacity, all measured indicators show significant changes. Shear viscosity and bulk viscosity decrease with increase in deviatoric stress and this tendency accelerates while approaching failure. Permeability also decreases throughout the test and during each creep stage due to the compaction of the specimens. The acoustic emission activity, in general, is found to be well correlated with the loading stages during the creep tests, accelerating closer to failure. The findings of this study can be used for the assessment of subcritical behavior of rock under different drainage conditions.

Name thesis:degree_name

M.S.

Level thesis:degree_level

Thesis

Discipline thesis:degree_discipline

Civil Engineering

Grantor

University of Illinois Urbana-Champaign

Year dc:date

2025

Author dc:creator

• Ding, Shirui

Contributors dc:contributor

• Makhnenko, Roman Y

• Time-dependent response
• Berea sandstone
• poro-visco-elasto-plastic behavior
• acoustic emission

Statement dc:rights

• Copyright 2025 Shirui Ding

Language dc:language

en

Handle dc:identifier

https://hdl.handle.net/2142/129157

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/129157