Civil and Environmental Engineering


First Advisor

Jongwan Eun

Second Advisor

Seunghee Kim

Date of this Version

Fall 12-2022


A THESIS Presented to the Faculty of The Graduate College at the University of Nebraska In Partial Fulfillment of Requirements For the Degree of Master of Science, Major: Civil Engineering, Under the Supervision of Professors Jongwan Eun and Seunghee Kim. Lincoln, Nebraska: December, 2022

Copyright © 2022 Jose Maria Ferdinand V. Calaunan


Nowadays, the permanent disposal of high-level radioactive waste materials has been a primary concern in several countries. The deep geological repository, being the preferred disposal method across the globe, utilizes a network of engineered barriers to prevent the radioactive material from spreading throughout the facility and harming the natural environment. Part of this engineered barrier system (EBS) is the buffer material, which essential function is holding the radioactive waste-containing canister in place. However, the potential generation of desiccation cracks in this buffer material is imminent due to the heat emitted from the radioactive waste. Knowing the capability of inorganic fibers to help mitigate such a situation, glass microfiber is proposed as a reinforcement material to bentonite, owing to its high heat resistance. This research aims to evaluate the effect of fiber content on bentonite in terms of swelling pressure and shear strength. Using the one-dimensional consolidation test setup, the swelling pressure test was conducted at both ambient and elevated temperatures to obtain the swelling pressure and compressibility characteristics of the inorganic-microfiber reinforced bentonite. Moreover, the shearing behavior of the bentonite sample was observed through the direct simple shear test. Lastly, the specimen’s behavior under the critical state was predicted using the Modified Cam Clay Model. The results obtained from this study would be a valuable tool for the baseline assessment of the effectiveness of the fiber reinforcement to potentially improve the engineering performance of the deep geological repository for the safe storage of high-level radioactive waste materials.

Advisors: Jongwan Eun and Seunghee Kim