在台灣河川坡陡流急的特殊地形及南北向主要交通系統下，構築於河道中的橋墩、橋台等結構物數量眾多，而這些水中結構物每於颱洪暴雨期間在河川水位迅速漲落下，常於橋墩底床發生劇烈淘刷導致橋墩基礎受侵蝕，造成橋墩裸露的危險。
對於橋墩沖刷防制工法的研究上，前人多以實驗室之試驗渠道進行試驗研究，鮮少於實際河道中做過相關試驗以瞭解實際設置的可行性及防制成效之研究，讓許多有別於現行常用之保護工法的研究止於理論。本研究致力於實際河道中設置筐網結構物保護工，以探討在各種不同筐網型式、設置距離及筐網結構物排列方式下對保護橋墩沖刷之影響，藉由改變筐網設置距離、筐網型式與排列方式的不同，作以下的討論： (1) 筐網設置距離與排列方式之探討、(2) 筐網設置距離與排列方式對流速衰減率之探討、(3) 筐網製作型式不同對流速衰減率之探討、(4) 筐網保護機構於其他河道之實驗結果，再根據筐網結構物不同的設置條件，找出其對橋墩沖刷防制的最佳佈置方式。
根據實驗結果得知，筐網結構物設置距離橋墩1倍橋墩直徑處、筐網型式為雙層及排列方式為倒三角形時，對水流流速衰減率可達70%以上，使到達橋墩前流速所產生之向下水流強度衰減，及橋墩兩側因筐網導流及遮蔽效應使馬蹄型渦流強度減弱，進而對橋墩周圍之底床泥砂起動能力不足，使橋墩周圍之局部沖刷量最小，防制效果最佳。

Because of the rapid flow of rivers which have steep slope and the east-west traffic system in Taiwan, there are numerous structures built in river course, such as bridge and abutment. These structures are usually in the danger of being destroyed since water elevation rise and fall fast during the storm period. For instance, the bridge pier will be imperiled when bed scour develops rapidly and causes pier to be exposed, after a flood goes by.
Previous study of pier scour countermeasure used to using physical model for simulation in laboratory channel, and seldom performed field experiment in river to figure out the feasibility and the effect of scour countermeasure. Therefore, some researches of new countermeasures, which are different from present common ones, were only on theoretical step.
The major work of present study was to investigate the influence of porous structure used to prevent scour by changing its distance from pier, formation of structure and arrangement. Some subjects were studied as follows: (1) the distance from pier and arrangement of a porous structure group; (2) relation between the above-mentioned two parameters and the velocity-decrease rate; (3) the relation between the porous structure formation and velocity-decrease rate; (4) the other results of experiment performed in other river. According to field experimental result, the best disposition for resisting pier scour was figured out.
From the results, velocity-decrease rate reached and surpassed 70% when distance from pier was one time the diameter of pier, the structure formation was double layer, and the group arrangement was an inverted triangle form. In this situation, the down-flow strength was decreased in front of the pier. The strength of horseshoe vortex around pier was also diminished because of the flow diversion and shelter effect of porous structure, therefore, the flow was insufficient for moving sediment of bed around bridge pier. The scour depth was smallest in this case, in another word; the protective effect was the best.

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