天然河道由於橋樑橋墩的設置使得通水面積減少、流場發生變化，進而改變原始的輸砂特性，因此導致橋墩周圍發生局部沖刷現象。當保護工設置於橋墩上游時會開始對橋墩沖刷產生影響。所以，本篇研究主要乃採用筐網結構物來減少橋墩周圍的局部沖刷。
　　本文主要探討筐網群結構物對橋墩沖刷保護之影響，藉由實驗改變筐網群設置距離、高程及筐網與筐網設置間距，另外針對筐網不同排列方式及設置數量，作一系列的討論： (1)沖刷歷程、(2)橋墩周圍底床高程、(3)筐網周圍底床高程、(4)橋墩周圍最大與最小沖刷深度位置及(5)保護效果。
　　根據試驗結果得知，筐網群設置距離橋墩5倍橋墩直徑處，筐網群底部設置於底床砂面上方0.15倍水深時，保護效果可達到85.88%，為本文試驗條件範圍內筐網最佳的佈置方式。

　Because the establishment of the pier of the bridge makes the area of water cross-section reduce on the natural river, flow field change, and then change primitive sediment transport characteristic, therefore result in local scour phenomenon around the pier. When protective structure is set up upstream of pier will begin to effect pier scour. So this paper uses mainly the Porous Structure groups to reduce local scour around the pier.
　This paper research into the protective effect of Porous Structure groups for pier scour mainly, through experiment change Porous Structure groups set up distance, height, Porous Structure and Porous Structure set up interval, then change Porous Structure different arrangement the way and different Porous Structure set up the quantity in addition, perform for a series of discussions. (1) Scouring processes, (2) Bottom bed height around the pier, (3) Bottom bed height around the Porous Structure, (4) Pier the minimum and maximum scour depth position and (5) Protective effect.
　According to the results of experiment, the Porous Structure groups set up 5 times diameter of the pier from the pier and Porous Structure groups bottom is set up 0.15 times of depth of water from the sediment of the bottom bed above, Porous Structure groups can provide for protective effect of pier to attain to 85.88%, for Porous Structure set up the way best in the experimental condition range of this paper.

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