Study on the development of volume reduction techniques of dredged material using ultrasonic

2020 Fiscal Year Final Research Report

• Project/Area Number: 18K04358
• 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: Tokuyama College of Technology
• Principal Investigator: UE SHUNJI 徳山工業高等専門学校, 土木建築工学科, 嘱託教授 (30124093)
• Project Period (FY): 2018-04-01 – 2021-03-31
• Keywords: 超音波 / 浚渫土 / 減容化

Outline of Final Research Achievements

For the purpose of developing technology for practical application of volume reduction of dredging degree deposited in water, using a newly prototyped ultrasonic irradiation device and practical size test container, fine particle size (silica stone powder, Clarified the volume reduction characteristics of silica sand). In the experiment, ultrasonic waves were radiated from the horizontal direction to the fine-grained soil put into water, the frequency was 30 to 40kH, the irradiation time was 15 to 30minutes, and the wetdensity ,water content ratio, dry density, gap ratio after the test, The relative density and volume reduction rate were calculated. As a result, the output voltage became maximum at a frequency of 30kHz and an irradiation time of about 30 minutes, the relative density was 90%, and the volume reduction rate was 34%, which was a good result for the plactical application of the volume reduction technol-ogy for underwater sediment dredged soil.

Free Research Field

地盤工学

Academic Significance and Societal Importance of the Research Achievements

超音波を水中に照射し、水中を伝わる微小振動を細粒材料に充てると個々の細粒材料が水中で微小振動し、水中を沈降、堆積する過程で粒子の粒子間の空隙を埋めるように再配列が進行し密度が増加し、容積の縮減が生じる。今回の研究が新規性を有する理由は材料が従来の大きさではなく細粒材料の大きさに対応する超音波周波数と音の大きさの関係を特定し、水中で超音波によって細粒材料の減容化率30%以上を可能にした方法と装置である点にある。加えて、それを可能にした振動子固定フリーに近い超音波振動子の開発があったことで実現できたもので、従来にない水中における細粒材料の減容化（高密度化）の方法と装置として新しい新規性を有する。