Study on the method of increasing compaction density of clayey soil

2022 Fiscal Year Final Research Report

• Project/Area Number: 20K04693
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 22030:Geotechnical engineering-related
• Research Institution: Osaka Metropolitan University College of Technology
• Principal Investigator: NIIRO Tadashi 大阪公立大学工業高等専門学校, その他部局等, 教授 (70198422)
• Project Period (FY): 2020-04-01 – 2023-03-31
• Keywords: 締固め / 粘性土 / 物理化学的作用 / チオ硫酸ナトリウム / アニオン性界面活性剤 / 堤防 / 盛土 / 埋戻し

Outline of Final Research Achievements

In this study investigated the effect of increasing the compaction density by adding inorganic and surfactant aqueous solutions to the mixed soil of four types of clay minerals (Na-type bentonite, Ca-type bentonite, kaolinite and allophane) and silica sand No. 7. As a result, it was confirmed that sodium thiosulfate increases the compaction density especially for Na-type bentonite mixed soil. In addition, the mechanism of the increase in compaction density was considered from the unconfined compressive strength characteristics and the effect of swelling was also investigated. Finally, we conducted an experiment assuming the backfilling work of the buried pipe outdoors, confirmed the effect of increasing the compaction density, observed the change over time of the cohesion c and the internal friction angle φ, and could be put to practical use showed high potential.

Free Research Field

地盤工学

Academic Significance and Societal Importance of the Research Achievements

粘土分が多く混じる土のせん断強さには，粘土鉱物特有の物理化学的性質が強く関係するため、締固め仕事量を大きくしても締固め密度を高めることはできない。そのために土質材料としての活用が制限されてきた。本研究はこの問題を改善する物理化学的方法を明らかにしたものであり、学術的意義がある。この成果が実用化され、粘土分が多く混じる土を容易に活用できるようになれば、有用土砂の種類拡大のみならず、降雨や地震に対して粘りと高い遮水性を有する盛土構築が期待できる。