Dynamic mechanical behavior of frozen Ottawa sand subjected to high strain rate loading

Aza-Gnandji, Cocou Davis Ruben

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https://hdl.handle.net/2142/130043 Copy

Description

Title

Dynamic mechanical behavior of frozen Ottawa sand subjected to high strain rate loading

Author(s)

Aza-Gnandji, Cocou Davis Ruben

Issue Date

2025-07-17

Director of Research (if dissertation) or Advisor (if thesis)

Baser, Tugce

Doctoral Committee Chair(s)

• Baser, Tugce
• Elbanna, Ahmed

Committee Member(s)

• Carroll, Chris
• Ehrhardt, David
• Hashash, Youssef

Department of Study

Civil & Environmental Eng

Discipline

Civil Engineering

Degree Granting Institution

University of Illinois Urbana-Champaign

Degree Name

Ph.D.

Degree Level

Dissertation

Keyword(s)

Frozen Ottawa sand, Split Hopkinson Pressure Bar, temperature-controlled chamber, high strain rate, impact loading, dynamic mechanical behavior, numerical simulations, high-speed infrared camera

Abstract

Increasing temperatures in the Arctic region raise environmental concerns, but also bring new opportunities for civil engineers including infrastructure development, such as roads, buildings, and pipelines, etc. Extensive research focusing on the behavior of frozen soils under quasi-static loading resulting in small strain rates exist; however, limited studies have explored their behavior under high strain rate loading, which is relevant in construction and resource extraction, etc. This research aims to investigate the dynamic mechanical behavior of frozen sands under varying thermal conditions and to characterize the impact of high strain rates on the overall stress-strain response. Frozen Ottawa sand samples having different dry densities and initial degrees of saturation were tested at temperatures of -15, -10, and -5°C to characterize the mechanical behavior. These samples were subjected to strain rates ranging from 400 to 1500/s using both traditional and modified Split Hopkinson Pressure Bar (SHPB). A temperature-controlled chamber was designed and attached to the SHPB setup to maintain constant temperatures during the experiments. A high-speed infrared camera was integrated to monitor temperature variations during the impact tests for estimating the thermal energy during the tests. The stress-strain curves of frozen Ottawa sand at different temperatures were obtained, and the results indicated that the stress-strain behavior was significantly influenced by the strain rate, temperature, and initial degree of saturation of the frozen sands. Specifically, the stress-strain curves exhibited peak stresses followed by pronounced strain softening when the strain rate was less than 900/s. However, at strain rates above 900/s, relatively more brittle response was observed. The results also revealed that the strength of the frozen Ottawa sand increased as the temperature decreased, due to the enhanced bonding between the ice and soil particles. To further evaluate the behavior of frozen sands under various strain rates, numerical simulations using LS-DYNA were performed. Two numerical methods available in LS-DYNA, namely, the Finite Element Methods and the Smoothed Particle Hydrodynamics, were employed to perform the numerical simulations of the SHPB tests. Holmquist-Johnson-Cook material model was employed in the simulations. Both numerical schemes produced results that were in good agreement with the experimental results. They also revealed the need for the development of advanced material models for the simulations of the dynamic behavior of frozen soils under extreme loading conditions. Key experimental results of this study can contribute to the design of infrastructure and protective structures that may be subjected to high-strain-rate deformations, impact loadings, or explosions. Future research will build on this study to develop a material model with temperature-dependent parameters for simulating the thermo-mechanical behavior of frozen sands under different thermal and extreme loading conditions.

Graduation Semester

2025-08

Type of Resource

Thesis

Handle URL

https://hdl.handle.net/2142/130043

Copyright and License Information

Copyright 2025 Cocou Davis Ruben Aza-Gnandji

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