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  • 學位論文

模型試驗探討地工合成材加勁壁壘結合格子壩於土石流防治之研究

Model Test on Geosynthetic-Reinforced Barrier with Grid Dam for Debris Flow Control

指導教授 : 陳榮河
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摘要


本研究利用室內砂箱模型試驗模擬土石流衝擊地工合成材加勁壁壘(Geosynthetic-Reinforced Barrier)以及加勁壁壘結合格子壩之兩種情況。研究係透過質點影像速度法(Particle Image Velocimetry, PIV)分析土石流之前端速度,及質點追蹤速度法(Particle Tracking Velocimetry, PTV)分析土石流之平均速度,並藉由兩種速度分析法觀察土顆粒在流動至撞擊過程的位移。同時,藉由荷重計量測背填土所受的衝擊力,探討灌漿面板及加勁材降低衝擊力的效果。 研究結果發現,灌漿面板式加勁壁壘受土石流衝擊後,背填土之受力均很小(最大值僅0.6 N),而磨損與變形亦小。基礎附近覆土之淘刷與堆積深度分別為2.18 cm、5.22 cm。而利用PIV測得土石流前端速度介於2.43-3.16 m/s,PTV得到平均表面流速為2.01-3.12 m/s;以前端速度略大於平均流速。此兩者透過因次分析轉換成現地流速符合一般之土石流流速。 另一方面,增設格子壩時,粗、細顆粒分離及土、水分離效果均提高,被攔阻在壩上游處之堆積量由5.0%增至47.2%,而堆積坡度則減緩至約5°,此將降低後續土石流之衝擊力。壩下游處淘刷量也因增設格子壩減少30.7%,可以保護基礎。然有效之土水分離也使得通過格子壩後之流速增加、堆積量減少,須加注意。 此外,將前人所作回包式與黏接式加勁壁壘與本研究灌漿式面板之加勁壁壘進行比較,發現在變形與磨損部分,以剛性之灌漿面板表現良好;在抵抗基礎淘刷及堆積方面,以回包式柔性的結構為佳。因此建議針對壁壘不同的位置可考慮採用不同型式,以達對抗土石流衝擊之最佳效果。

並列摘要


A small-scale model test was conducted to simulate debris flow impacting a geosynthetic-reinforced barrier with a grouted facing-panel, as well as the barrier constructed with a grid dam. The analyses of the front velocity of the flow and its average velocity were performed by particle image velocimetry (PIV) and particle tracking velocimetry (PTV). The movement of the particles was the obtained through the analysis of these velocities. Impact force behind the panel (in the backfill) was measured by load cells to explore the effect of the panel and the reinforcement in reducing the impact force from the flow. From the test results, it was found that the impact force behind the panel was generally small (the maximum value was only 0.6 N), and the abrasion and deformation of the panel were slightly. The final scouring and deposition depths were 2.18 cm and 5.22 cm, respectively. The average velocity of the debris flow was 2.01-3.12 m/s, which was slightly less than the front velocity, 2.43-3.16 m/s. These values of velocity, if converted into the prototype velocity by dimensional analysis, are in the general range of the velocity of debris flow. With the addition the grid dam, the separation of coarse and fine particles, as well as the separation of soil and water, was good. As a result, particles accumulated in the upstream of the barrier were increased to 47.2 % from 5% when no grid dam existed, and the slope gradient was decreased to about 5, which would reduce the impact of future debris flow. The depth of scouring in the downstream of the barrier also decreased 30.7%. However, the effective soil-water separation made the flow increased velocity and accordingly reduced particles deposited. Moreover, compared to the wrap-around and glued types of barrier, the grouted panel had good performance in resisting deformation and abrasion from debris flow. On the other hand, the wrap-around type performed better in resisting scouring because of its flexible structure. This suggests that different types of facing may be used at different locations of a barrier to achieve best performance in resisting the impact of debris flow.

並列關鍵字

Geosynthetics barrier debris flow model test grid dam

參考文獻


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