| Project/Area Number |
23KF0239
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| Research Category |
Grant-in-Aid for JSPS Fellows
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| Allocation Type | Multi-year Fund |
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| Section | 外国 |
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| Review Section |
Basic Section 22030:Geotechnical engineering-related
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| Research Institution | Kyoto University |
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Principal Investigator |
勝見 武 京都大学, 地球環境学堂, 教授 (60233764)
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| Co-Investigator(Kenkyū-buntansha) |
ZHANG XUDONG 京都大学, 地球環境学堂, 外国人特別研究員
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| Project Period (FY) |
2023-11-15 – 2026-03-31
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| Project Status |
Granted (Fiscal Year 2023)
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| Budget Amount *help |
¥1,900,000 (Direct Cost: ¥1,900,000)
Fiscal Year 2025: ¥1,000,000 (Direct Cost: ¥1,000,000)
Fiscal Year 2024: ¥500,000 (Direct Cost: ¥500,000)
Fiscal Year 2023: ¥400,000 (Direct Cost: ¥400,000)
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| Keywords | Vacuum preloading / Particles clogging / DEM-LBM / Coupled modeling / Vertical drain |
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| Outline of Research at the Start |
健全な社会基盤構造物の構築には、適切な地盤挙動の制御が必要であり、軟弱な粘土地盤上に構造物を建設する場合は、鉛直荷重による沈下が懸念となる。本研究では、地盤に排水材を挿入し地上部から吸引することで粘土地盤からの排水を促し、構造物の建設前に予め粘土地盤を圧縮させておく真空圧密工法を対象に、当該工法で用いられる排水材の目詰まり形成メカニズムの解明を目的とする。具体的には、室内土槽試験で目詰まりの形成要因を明らかにし、得られた実験結果を、離散要素法（DEM）と数値流体力学の一つである格子ボルツマン法（LMB）を組み合わせた数値解析で再現して目詰まりの影響因子を究明し、効果的な対策法の提案につなげる。
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| Outline of Annual Research Achievements |
In the field of environmental geotechnics, the vacuum preloading technique is a widely used method, which is always applied to the soft soil-like foundations’ improvement and accelerates the soil’s dewatering and vacuum consolidation. However, the clogging problem would reduce the efficiency of dewatering. We have conducted this research by literature investigation and numerical modeling development. In this year's research, the problems of vacuum drainage clogging are comprehensively summarized. The main clogging types in recent years have been summarized, in which the membrane clogging played an important role in clogging. The influence factors of drainage clogging have been completely discussed. The numerical modeling methods were explored to achieve this process simulation. The results indicated that soil particle motion is successfully described by the DEM. Regarding the soil-water interaction simulation, and the LBM-DEM has been explored as a novel method to simulate the particle-water interactions. The result indicated that particles could form a kind of arch structure clogging the membrane orifice. The formation of the clogging arch prevented the discharge of soil particles and greatly decreased the fluid velocity. Notably, the fluid velocity distribution around the orifice is in a certain shape according to the velocity of the LBM cells. The size of the shape regularly changes with the distance to the membrane orifice.
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| Current Status of Research Progress |
Current Status of Research Progress
2: Research has progressed on the whole more than it was originally planned.
Reason
This research consists of three sub-themes: 1, To study the occurrence of particles clogging during the seepage by DEM-LBM coupled modeling. 2, To study the clogging arch of the polydispersed particle system at the orifice. 3, Validation of multiscale analysis. In this year's research, a lot of literature has been organized, in which some evidence has proved that clogging could occur in different conditions, including membrane clogging and particle clogging. Through the literature review, we concluded that membrane clogging should play an important role in the clogging effect. In addition, the coupled method has already been studied. The soil particle generation was tested based on DEM. The particles of different sizes could be generated randomly in a certain volume. The liquid could be simulated with the assistance of the Lattice Boltzmann Method, and the interaction between water and particles could also be achieved. At present, the methods have almost tested well during the past several months. Therefore, we are going to explore the occurrence of particles clogging during the seepage preliminarily. Since the membrane micromorphology is complex, we are conducting the simulation in detail on the one-orifice simplified condition.
As mentioned above, we assess that the study overall went well.
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| Strategy for Future Research Activity |
In future research, we will continue to explore the mechanism of clogging under vacuum preloading by numerical analysis under different membrane conditions. In the engineering practice, not only the membrane filter pore size but also the pores distribution effect should be considered. Regarding this research, we are going to figure out the clogging features of the soil particles to the orifice through the coupled simulation, so that the goal of micro-mechanism can be achieved, which is hard to observed by the existing experiments. Also, if possible, we will make different simulations to investigate the clogging effects. Apart from that, we will consider the comparisons with previous experimental results of vacuum preloading from different researchers for the preliminary validation reliability of the novel coupled method.
In addition, we are going to test the clogging modeling method in some other related fields, exploring a similar clogging effect in the fields of environmental geotechnics or earth science, such as the interface between the soil particles and geosynthetic sorption sheet against natural heavy metal contamination.
Besides, we plan to summarize the mechanism analysis results of the simulations in the next fiscal year, write a paper, and publish it in international journals in 2024.
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