| 粗度係数 n (水理公式集) |
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| 材料 |
水路の形式 |
nの範囲 |
nの平均値 |
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| 真ちゅう |
暗渠 |
0.009〜0.013 |
0.010 |
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| 溶接鋼管 |
0.010〜0.014 |
0.012 |
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| リベット鋼管 |
0.013〜0.017 |
0.016 |
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| 鋳鉄(塗装) |
0.010〜0.014 |
0.013 |
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| 鋳鉄(塗装なし) |
0.011〜0.016 |
0.014 |
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| コルゲート鋼管 |
0.021〜0.031 |
0.024 |
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| 合成樹脂 |
0.008〜0.010 |
0.009 |
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| ガラス |
0.009〜0.013 |
0.010 |
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| モルタル |
0.011〜0.015 |
0.013 |
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| コンクリート |
0.010〜0.020 |
0.014 |
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| 素焼き土管 |
0.011〜0.017 |
0.013 |
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| 上薬した土管 |
0.011〜0.017 |
0.014 |
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| レンガ積み、モルタル仕上げ |
0.012〜0.017 |
0.015 |
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| 底を仕上げた下水渠 |
0.016〜0.020 |
0.019 |
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| 鋼、塗装なし、平滑 |
ライニングした水路 |
0.011〜0.014 |
0.012 |
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| モルタル |
0.011〜0.015 |
0.013 |
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| 木、かんな仕上げ |
0.012〜0.018 |
0.015 |
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| コンクリート、コテ仕上げ |
0.011〜0.015 |
0.015 |
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| コンクリート、底面砂利 |
0.015〜0.020 |
0.017 |
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| 石積み、モルタル目地 |
0.017〜0.030 |
0.025 |
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| 空石積み |
0.023〜0.035 |
0.032 |
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| アスファルト、平滑 |
0.013 |
0.013 |
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| 土、直線、等断面水路 |
ライニングなし水路 |
0.016〜0.025 |
0.022 |
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| 土、直線水路、雑草有り |
0.022〜0.033 |
0.027 |
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| 砂利、直線水路 |
0.022〜0.030 |
0.025 |
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| 岩盤、直線水路 |
0.025〜0.040 |
0.035 |
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| 整正断面水路 |
自然水路 |
0.025〜0.033 |
0.030 |
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| 不整正断面、雑草、立ち木多し |
0.075〜0.150 |
0.100 |
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