Fluid Flow in Disrupted Porous Media: Volcanological and Radiological Waste Applications

This dissertation is focused on numerical simulations of transient hydrogeologic settings in which a previously stable system is subjected to a sudden perturbation. Disruptions of hydrogeologic systems force an adjustment in fluid (groundwater, air, and water vapor) flow that yields a new, distinct state from the prior steady system. Three major types of disruption are considered in specific scenarios for this work: (1) Fracturing of a porous medium, resulting in a free exit and rapid drainage of water; (2) Changes in the structure of the porous medium, resulting in large differences in groundwater flow and, of particular interest, challenges in numerical modeling of such systems; and (3) Addition of a strong heat source in systems, resulting in thermal-hydraulic-chemical-mechanical changes and a consequent alteration of the porous medium. In 2007, two phreatic eruptions occurred at Nevado del Huila Volcano, Colombia in which deep , elongate fissures developed and large lahars were released. Subsequent research suggested that water in these lahars originated as groundwater inside the volcano . Chapter 2 of this dissertation applies the numerical model FEHM (Finite Element Heat and Mass) to a conceptual model for these emissions in which the fissures formed with a free exit at their topographically lowest point, allowing water to pass through the walls of the fissure and escape out the free exit. The large surface area and high pressure gradient between the hydrostatic­ pressure porous medium and the suddenly imposed atmospheric pressure boundary allows high discharge rates and the release of a volume of water that, when accounting for post-lahar bulking, could reasonably form the observed Huila lahars . The second major component of this dissertation concerns ongoing research in radiogenic waste disposal in salt. Recent investigative efforts have led to the development of a concept for disposal of high-level radioactive waste in "drifts," or galleries carved into bedded salt. These drifts are then back-filled with crushed, mined salt and abandoned, with viscoplastic closure of the drift ensuring the long-term isolation of the radioactive source. As an element of this research, a first-ever drift-scale experiment was built and activated in September, 2017. Numerical simulations have been integral to the design, implementation, and real-time assessment of the experiment. Chapter 3 presents a new, porosity-dependent retention function that was built into FEHM for use in modeling of heated salt systems. Brine, vapor, and heat transport can cause the dissolution or precipitation of salt and lead to strong porosity changes. Neglecting these porosity variations during the course of a simulation run can cause incorrect, unphysical model behaviors which are addressed by the new retention function. Chapter 4 then applies the new function to simulations for the purpose of predicting and evaluating the ongoing experiment.

Grantor dc:publisher

State University of New York at Buffalo

Year dc:date.issued

2018

Author dc:creator

• Johnson, Peter Jacob; 0000-0001-7491-8883

Contributors dc:contributor

• Valentine, Greg
• Geology

• geology
• hydrologic sciences

Statement dc:rights

• Users of works found in University at Buffalo Institutional Repository (UBIR) are responsible for identifying and contacting the copyright owner for permission to reuse. University at Buffalo Libraries do not manage rights for copyright-protected works and cannot assist with permissions.
• Copyright retained by author.

Language dc:language

eng

Handle dc:identifier

http://hdl.handle.net/10477/77959

OAI record oai:identifier

https://ubir.buffalo.edu/oai/request?verb=GetRecord&metadataPrefix=qdc&identifier=oai%3Aubir.buffalo.edu%3A10477%2F77959