Featured
Geotechnical engineering for carbon reduction and geohazard mitigation

• • As environmental challenges caused by climate change have become a global concern, the need for sustainable and resilient geotechnical solutions is increasingly emphasized. In particular, bio-geotechnics can help reduce carbon emissions from construction activities, while direct carbon storage in the subsurface can mitigate carbon emissions from broader industrial activities.
  • Geohazards such as earthquakes and landslides have caused significant loss of life and property damage. As unbanization and climate change continue to amplify these risks, the importance of effective mitigation strategies becomes even more critical. Geotechnical engineering plays a fundamental role in mitigating the risks associated with geohazards.
  • Geo-Energy laboratory, led by Prof. Kwon, focuses on the development of sustainable bio-geotechnics, energy geotechnology, and mitigation of risks for geohazards. The detailed research interests are as follows:

Microbially Induced Calcium Carbonate Precipitation (MICP)

• • Microbially induced calcium carbonate precipitation (MICP) is a versatile biogeotechnical method being developed for ground improvement in geotechnical engineering. The MICP process involves the microbial hydrolysis of urea by bacteria such as Sporosarcina pasteurii, which generates carbonate ions (CO3^2-) from urea ((NH2)2CO). These carbonate ions then interact with externally introduced calcium ions (Ca²⁺), leading to the formation of calcium carbonate (CaCO3). Thus, the technology can serve as an alternative to construction activities that use cement materials, which contribute to the increase in CO2. precipitation process enhances the mechanical properties and impermeability of soil. Reductions in permeability due to MICP, precipitation patterns, and enhanced strengths are representative findings.

Microbially induced biopolymer formation (MIBF) and enzyme-induced biopolymer formation (EIBF)

• • Microbially induced biopolymer formation (MIBF) is a process in which microorganisms synthesize extracellular polymeric substances (EPS) or biopolymers as part of their metabolic activities, thereby modifying soil properties. These biopolymers can occupy soil pores, reducing permeability (bioclogging), or bind soil particles, enhancing soil strength (biostabilization). Enzymatically induced biopolymer formation (EIBF), in contrast, employs enzymes rather than living microorganisms to stimulate biopolymer synthesis in porous media such as soil. This approach utilizes specific enzymes, such as dextransucrase, to catalyze the formation of insoluble biopolymers like dextran from appropriate substrates. Ground improvement using biopolymers is considered a sustainable technology, which is environmentally-friendly and economic compared to chemical grouting. Our study provides a comparison of MIBF and EIBF and clogging behavior for both methods.

Carbon mineralization for geological carbon storage

• • Geological carbon storage is a method of storing CO2 within host rock formations. Under extreme pressure and temperature, which is common for deep reservoir conditions, CO2 is stored in a supercritical phase; however, it always carries a potential risk of leakage due to buoyancy and geological activities such as earthquakes. Carbon mineralization is a promising way of geological carbon storage, in which CO2 is stored in the form of carbonate minerals. Process of carbon mineralization can be summarized as follows: (1) CO2-dissolved (acidic) water is injected into host rock formations, (2) the acidic solution reacts with silicate minerals in the host rock, leading to an increase in concentration of divalent cations (Ca²⁺, Mg²⁺, Fe²⁺), (3) the divalent cations react with carbonate ions to form carbonate minerals such as calcite (CaCO3), magnesite (MgCO3), siderite (FeCO3). Mafic rocks such as basalt are considered potential host formations for carbon mineralization since it has abundant divalent cations. Effects of flow rates on mineralization pattern and changes in hydraulic properties were investigated.

Landslides

• • Landslides are natural geohazards characterized by the downslope movement of earth materials, including soil, rock, and debris, typically triggered by heavy rainfall. These events can result in severe damage to infrastructure and significant casualties. Research interests related to landslides include mitigating landslides (debris flow) risks, assessing landslides damage using remote sensing, and prediction of geohazards by statistical algorithm. Numerical and experimental studies have been conducted to investigate the effective location and arrangement of countermeasures for effective mitigation. UAV-LiDAR-based remote sensing enables accurate estimation of topographic changes in actual landslide field. These studies contribute to the development of effective risk management strategies.

Further readings:

• • Baek, S. H., Hong, J. W., Kim, K. Y., Yeom, S., & Kwon, T. H. (2019). X‐ray computed microtomography imaging of abiotic carbonate precipitation in porous media from a supersaturated solution: Insights into effect of CO2 mineral trapping on permeability. Water Resources Research, 55(5), 3835-3855.
    Baek, S. H., Kwon, T. H., & DeJong, J. T. (2024). Reductions in hydraulic conductivity of sands caused by microbially induced calcium carbonate precipitation. Journal of Geotechnical and Geoenvironmental Engineering, 150(2), 04023134.
    Choi, S. K., Park, J. Y., Lee, D. H., Lee, S. R., Kim, Y. T., & Kwon, T. H. (2021). Assessment of barrier location effect on debris flow based on smoothed particle hydrodynamics (SPH) simulation on 3D terrains. Landslides, 18, 217-234.
    Choi, S. K., Ramirez, R. A., & Kwon, T. H. (2023). Acquisition of high-resolution topographic information in forest environments using integrated UAV-LiDAR system: System development and field demonstration. Heliyon, 9(9).
    Ham, S. M., Martinez, A., Han, G., & Kwon, T. H. (2022). Grain-scale tensile and shear strengths of glass beads cemented by MICP. Journal of Geotechnical and Geoenvironmental Engineering, 148(9), 04022068.
    Kim, Y. M., & Kwon, T. H. (2023). Engineered bioclogging in sands: comparison of microbially induced and enzyme-induced biopolymer formation. Géotechnique, 1-14.