以數值模擬探討不透水布對壩下沖刷坑之滲流影響

Numerical Assessment on Effects of Impermeable Coating on the Seepage flow below a Scour under Sabo Dams

許少華(Shaohua Marko Hsu) ； 蘇重光(Chong-Gaung Su) ； 林伯聰(Bor-Tsong Lin)

《中華水土保持學報》 29卷1期 (1998/03) Pp. 1-10

https://doi.org/10.29417/JCSWC.199803_29(1).0001

摘要

攔砂壩設施爲集水區上游水土保持工作中一種重要的工程手段。在台灣，常因壩下游之保護工遭受沖刷而致破壞，本文回顧了沖刷坑的形成理論，以砂箱試驗的結果來決定沖刷坑的幾何形狀，並以試驗所測得之坑壁壓力分佈作爲滲流模型之一個邊界條件。滲流模擬之結果，可進一步瞭解沖刷坑附近之滲流流場。壩上游若以不透水布覆蓋，則可減低壩址附近之滲流力（水力坡降）約二至三成，然不透水布長度若增至一定限度以上。其邊際效益即平緩下來，此一性質可提供給設計者參考。

關鍵字

不透水布 ； 攔砂壩 ； 沖刷坑 ； 滲流力

並列摘要

Saba dam is an important engineering measure for soil conservation in upstream watershed. In Taiwan, damage of such dams occurs frequently due to scoured hole downstream of the dams. In this article, Theories of formation of such scour are reviewed. A numerical model solving Laplace equation by finite difference method within an irregular domain is constructed. The irregular shape of scoured hole and pressure along the hole are determined according to physical model in a sand tank. Simulation shows that seepage flow field is sensitive to both downstream pressure conditions and pressure distribution along the scour. Different seepage types are identified for cases with running water or still water in the scour. An impermeable coating paved on bed-surface upstream of dam can reduce outward seepage force acting along the scour to 70 % of the original value. The marginal benefit, however, slow down when the length of coating keep increase, which should be a benefit/cost consideration to designer of such measure.

並列關鍵字

Impermeable Coating ； Sabo Dam ； Scour Hole ； Seepage Force