| Project/Area Number |
07456104
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Irrigation, drainage and rural engineering/Rural planning
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| Research Institution | Niigata University |
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Principal Investigator |
YOSHIDA Shoji Niigata University, Faculty of Agriculture, Professor, 農学部, 教授 (80018530)
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| Co-Investigator(Kenkyū-buntansha) |
NAKANO Toshiro Niigata University, Faculty of Agriculture, Associate Professor, 農学部, 助教授 (40018544)
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| Project Period (FY) |
1995 – 1996
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| Project Status |
Completed (Fiscal Year 1996)
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| Budget Amount *help |
¥2,800,000 (Direct Cost: ¥2,800,000)
Fiscal Year 1996: ¥700,000 (Direct Cost: ¥700,000)
Fiscal Year 1995: ¥2,100,000 (Direct Cost: ¥2,100,000)
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| Keywords | pipe drain / paddy field / back filled trench / layred soil / numerical analysis / flow net / unsaturated flow / bearing capacity / 定常・非定常・浸透流解析 / 流線の数値解析 / 有限要素法 / 飽和-不飽和浸透解析 / TDR土壌水分計 / 水田の地耐力 / コーンペネトロメータ / 大区画化水田 / 地耐力 / 飽和-不飽和浸透流 / 負圧浸透 |
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| Research Abstract |
Recently in large sized paddy fields, the control of subsurface drainage due to pipe drainage is considered to be important. The matter of pipe drainage in paddy fields with layred soils, especially the drainage effects of the back filled trench, were investigated by means of numerical analysis due to the finite element method. The following results were obtained.
(1) We proposed the method of numerical analysis which can obtain not only the equipotential lines but also the stream lines in the steady-state Darcy flow throughout layred soils.
(2) By the numerical analysis, we found that hydraulic conductivity of both the back filled trench and the layr, which lie over the trench, largely affected the flow patterns and the discharge from drain pipe. For the numerical analysis, constant depth of ponding water at ground surface is upper boundary condition. As the lower boundary, we defined an impermeable layr, which is deeper than 1.0m.
(3) After the drainage of surface water, the draw down of the ground water level and the decrease of both the soil water contents and the pipe drain discharge were numerically analyzed.
(4) By the field observations, it was verified that in each of the plowed layr, the hard pan and the original sub layr the relationship between bearing capacity of soils and the soil water contents were linear, respectively.
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