At the 2023th Geotechnical Engineering Research Conference held from July 7th to 11th, 14, our university graduate students Minori Oki, Chinatsu Mioka, and Rikuto Fujikata received the Outstanding Paper Presenter Award. Did.

【Winner】
Minori Oki (Tokyo University of Marine Science and Technology, Graduate School of Marine Science and Technology, Master's Program, 2nd year, Department of Marine Resources and Environmental Studies）
Chinatsu Mioka (Tokyo University of Marine Science and Technology, Graduate School of Marine Science and Technology, Master's Program, 2nd year, Department of Marine Resources and Environmental Studies）
Rikuto Fujikata (Tokyo University of Marine Science and Technology, Graduate School of Marine Science and Technology, Master's Program, 1nd year, Department of Marine Resources and Environmental Studies）

[Title and content of award-winning research]
Minori Oki
Title: Experimental study of the drag reduction effect of soil particles in turbulent mudflow
Elucidation of the flow characteristics of turbulent mudflow, which is a type of density current and is a solid-liquid mixed phase flow of seawater and clay particles, is required for selecting offshore development sites and evaluating the stability of submarine infrastructure.Previous studies have reported that solid-liquid multiphase flow in a circular pipe has a drag reduction effect compared to single-phase flow, and changes in the turbulence structure, such as vortices caused by particles, are thought to be an example of the cause.On the other hand, in a study in which a density flow consisting of a quartz suspension and salt water was allowed to flow down by opening a partition in a water tank and the velocity of the trailing part was measured, it was found that if the density was the same, the trailing part of the quartz suspension It has been reported that the maximum flow velocity of water is higher than that of salt water, and it is inferred that the resistance reduction effect of soil particles is exerted even in turbulent mud flow.Therefore, in this study, we poured NaCl aqueous solution, silica suspension, and kaolin suspension of the same density into a water tank and investigated the drag reduction effect of soil particles in turbulent mudflow.

Chinatsu Mioka
Title: Literature survey on lifting of seabed mineral resources by capsule transportation
Capsule transport using a carrier material circulation method has been proposed as a lifting system for seabed mineral resources.This system circulates viscous fluid containing granules through an annular pipe consisting of a riser pipe and a downcomer pipe to transport minerals in capsules from the ocean floor to the ocean.However, in existing capsule transportation, the transport medium is water or air, and transport is mainly horizontal, so access to the intake port is not as difficult as in the deep sea.Therefore, we conducted a literature survey on the ``basic shape and attachments'' and ``intake mechanism'' of capsules suitable for ore lifting.

Rikuto Fujikata
Title: Evaluation of the effect of foundation rotation using transparent ground on the ground
One of the foundation penetration methods is the rotary penetration method, in which a spiral blade is generally attached to the tip of the foundation.Until now, there have been studies on the disturbance of the ground near the foundation by spiral blades, but the only effect that the rotation of the foundation itself has on the ground is that it is known empirically that the pile cap load decreases. The mechanism is not fully understood.In this research, we used transparent ground that can visualize arbitrary cross sections of the ground, and observed the distribution of displacement increments through image analysis in vertical and horizontal sections of the ground when penetrating a circular foundation at multiple rotation speeds. The distribution of the maximum shear strain increment and the distribution of volumetric strain increment were analyzed assuming a plane strain state.By comparing the obtained results with changes in pile cap load, we considered the effect of foundation rotation on the ground.

From left) Chinatsu Mioka, Rikuto Fujikata, Minori Oki

<Related links>
Japan Geotechnical Society HP
58th Geotechnical Engineering Research Presentation Website
58th Geotechnical Engineering Research Conference Excellent Paper Presenter Award Winner