Research Activities

The presence of heavy metals or metalloids and other trace elements in soils and rocks is not unusual; for example, arsenic concentrations in Japan are known to be higher than the global average. This is considered to be due to Japan's tectonic setting at the boundary between the continental and oceanic plates, where certain metals tend to accumulate because of melting-point and geochemical characteristics.

When highly concentrated, these metals can be valuable resources-mines are developed in such areas, and even hot spring waters often contain trace metals that provide benefits to our daily lives. On the other hand, ingestion or inhalation of heavy metals can pose health risks, and environmental standards such as leaching limits are defined by Japan's Soil Contamination Countermeasures Act.

In some cases, when soils or rocks containing naturally occurring heavy metals are excavated and exposed to air or water, oxidation can lead to metal leaching. However, most reported concentrations slightly exceed the regulatory limits. Considering Japan's limited land availability for soil disposal, the relatively low concentrations of naturally occurring metals, the fact that no health effects occur unless the substances are ingested or inhaled, and the importance of soil as a valuable resource, it is desirable to reuse excavated soils as geomaterials while carefully considering their environmental impacts.

In this research area, we collect soils and rocks generated from actual construction projects to examine their leaching characteristics, and we are developing rational countermeasures such as the attenuation layer method, aiming to establish practical and effective construction procedures.

• Zhang et al. (2026) Geotextiles and Geomembranes, 54(1), 1-13. View Paper
• Gathuka et al. (2022) Soils and Foundations, 62(3), 101130. View Paper
• Kato et al. (2021) Soils and Foundations, 61(4), 1112-1122. View Paper

With the revision of the Soil Contamination Countermeasures Act and the growing awareness of risk management, the number of identified soil contamination cases has been increasing. Although excavation and off-site removal of contaminated soils are commonly adopted countermeasures, it is preferable to manage such soils appropriately on-site to prevent secondary contamination. Various in-situ remediation techniques have therefore been developed and studied. For more than 20 years, our laboratory has been conducting research on containment technologies focusing on the soil-bentonite mixing (SBM) vertical cutoff wall, which is constructed by directly mixing bentonite into in-situ soils. We evaluate its performance in terms of both hydraulic barrier function and deformation compatibility.

Per- and polyfluoroalkyl substances (PFASs), which repel both water and oil, have been widely used as useful synthetic chemicals. However, their potential impacts on human health have become evident, raising serious concerns about groundwater and soil contamination. Unlike conventional organic contaminants, PFASs exhibit both hydrophobic and hydrophilic properties, and their behavior in geologic media remains insufficiently understood. To improve understanding of the reactivity between PFASs and soils, our laboratory conducts adsorption experiments using various types of soils.

• Chen et al. (2024) Geotechnical Engineering Challenges to Meet Current and Emerging Needs of Society, 2862-2865. View Paper
• Kato et al. (2025) Proceedings of Geo-EnvironMeet 2025, 100-105. View Paper
• Yamamoto et al. (2025) Japanese Journal of JSCE, 81(6), 00257. View Paper

Proper waste management is essential for sustaining social activities, and landfill sites-the final destinations for waste-require careful consideration of land availability and environmental safety. Our research group has studied these issues from a geotechnical perspective, including the development of construction techniques for pile installation on closed landfill areas. Recently, in view of the limited remaining capacity of existing landfill sites, we have investigated strategies for extending their service life. Specifically, from a geotechnical viewpoint, we examined the stability of waste deposits, and from an environmental chemistry perspective, we conducted leaching tests using medium-scale columns.

Frequent large-scale natural disasters, such as earthquakes, tsunamis, and heavy rainfall, have created an urgent need for more efficient management of disaster waste. After a disaster, various types of debris -such as plastics, wood fragments, and other materials- are often temporarily stockpiled in mixed conditions. Even the soil fraction recovered after sorting frequently contains fine impurities. When soils containing wood debris are reused as geomaterials, the biodegradation of organic matter over time can generate voids in the ground, potentially reducing its stability. Therefore, it is essential to establish treatment methods capable of achieving both high processing speed and accuracy. Our research focuses on developing rational approaches for sorting and processing large volumes of disaster waste to identify soil that can be safely reused as reconstruction material. We classify and analyze the types and quantities of waste before and after treatment to verify actual processing conditions. In recent studies, we also examined the effects of soil particle-size distribution and waste composition on treatment efficiency through laboratory and full-scale experiments.

• Sarmah et al. (2024) Waste Management, 182(15), 32-41. View Paper
• Takai et al. (2023) Proceedings of the 9th International Congress on Environmental Geotechnics, 1, 3-10. View Paper
• Sumikura & Katsumi (2022) Journal of Material Cycles and Waste Management, 24(4), 1216-1227. View Paper

Coupled issues of energy and geotechnical engineering, such as geothermal energy utilization, have recently attracted increasing attention. While many studies have investigated heat transfer processes in groundwater and soils, the environmental safety associated with temperature changes in the ground has not yet been fully clarified. Our laboratory aims to elucidate the effects of soil-heat interaction on the migration behavior of chemical substances in subsurface environments. To this end, we have improved conventional testing equipment and are conducting both experimental and analytical studies.

Climate change and global warming are urgent challenges that must be addressed. Our laboratory focuses on by-products generated from industrial and construction activities, and is developing technologies to achieve carbon neutrality through their effective utilization.

• Yu et al. (2024) Geotechnical Engineering Challenges to Meet Current and Emerging Needs of Society, 2739-2744. View Paper
• Kato et al. (2023) Soils and Foundations, 63(1), 101274. View Paper
• Sakr et al. (2022) Journal of Geotechnical and Geoenvironmental Engineering, 148(8), 04022061-1-13. View Paper