圓柱堆翻轉、變形破壞與流體化現象之輸送帶實驗分析

本研究以輸送帶渠槽帶動圓柱來進行實驗，以模擬斜坡上崩塌土體轉換化為土石流中間的過程。實驗分為微觀的翻轉破壞、結構變形破壞以及巨觀的流體化實驗三部分。在圓柱翻轉破壞實驗部分藉由四種不同速度(5.08、10.16、15.24和20.32cm/s)、五種坡度(0˚、5˚、10˚、15˚和20˚)搭配成各種不同實驗條件來進行，觀察其翻轉顆粒在翻轉前和翻轉瞬間的角速度、位移的微觀變化。結構破壞實驗主要探討的是微觀的顆粒旋轉變形破壞現象。藉由兩種輸送帶速度(4.17cm/s、12.34cm/s)以及兩種渠槽角度(0∘、20∘)搭配成四種實驗條件來進行。分析方法則是以粒子影像分析法為基礎，以分析圓柱堆破壞時、破壞中及破壞後之運動機制。由實驗分析結果顯示，無論在何種實驗條件下，圓柱堆結構破壞皆由底層圓柱受剪力而先產生破壞，外圍圓柱顆粒整體呈逆時針方向運動。輸送帶速度越大，造成圓柱堆底層剪力區範圍越大，角速度亦增加;渠槽角度越大，則造成圓柱堆自由表面顆粒向左側運動堆積。而流體化實驗部分則是利用兩種輸送帶速度(4.17cm/s、12.34cm/s)、五種(0˚、5˚、10˚、15˚和20˚)以及兩種隔板高度(2.2cm、3.8cm)與四種圓柱堆初始厚度(3D、5D、10D、13D)搭配成50組不同實驗條件來進行，並以圓柱基本運動型態與無因次流體化層厚度隨時間的變化量以及圓柱流出侷限區域之順序進行分析與探討，結果發現速度為12.34cm/s之圓柱堆基本運動型態不同於速度為4.17cm/s且進而影響流體化層厚度隨時間的變化量，使得相同坡度下、不同初始厚度之結果剛好相反。

關鍵字

圓柱翻轉；變形破壞；粒子影像分析；流體化；輸送帶

並列摘要

This study performs experimental work with cylinders on the conveyor belt to simulate the initial process of landslide induced debris flow.The experimental set up consists of three parts: microscopic overturn deformation and macroscopic fluidization. The kinetic of angular velocity and displacement of the overturn process on the top layer of the cylinders is studied. The change of porosity before and after the overturn is analyzed at different velocities (i.e. 5.08cm/s, 10.16cm/s,15.24 cm/s,20.32 cm/s), and slopes (i.e. 0°, 5°, 10°,15°, 20°),respectively. The particle image algorithm is used to study the deformation on the bottom of the assemble cylinders by shearing force. The change of porosity before and after the failure is analyzed at different velocities (i.e. 4.17cm/s, 12.34cm/s), and slopes (i.e. 0°, 20°). We establish a method to measure the deformation, angular velocity and porosity of particles. The experimental results show that region of the shearing zone increases as the velocity of the conveyor belt, increases. Different belt velocities (i.e. 4.17cm/s, 12.34cm/s) affect the thickness of fluidization, and lead to two opposite results on the decay rate of PVC, and steel layers under the same experimental conditions. The sequence of cylinders flowing out the confined zone is strongly related to the gap clearance. When the gap is raised, the leading side of cylinders will flow out first while the gap becomes low, the tailing side and bottom parts of cylinders will flow out first.

並列關鍵字

overturn ； cylinder ； conveyor belt ； particle image algorithm ； deformation ； fluidization

參考文獻

7. 周憲德、張藝耀，「斜坡堆積圓球及圓柱受水平振動時之傾斜角分析」，中國土木水利工程學刊，第十六卷，第一期，第145-154頁 (2004) 。

10. Capart, H., Young, D.L., and Zech, Y., “ Voronoï imaging methods for the measurement of granular flows , ” Exp. Fluids, Vol.32, pp. 121-135 (2002).

11. Dury, C.M., and Ristow, G.H., “Boundary effects on the angle of repose in rotating cylinders,” Physical Review E, Vol. 57, No.4, pp.4491-4496 (1998).

12. Denlinger, R.P., and Iverson, R.M., “Flow of variably fluidized granular masses across three-dimension terrain: 2.Numerical predictions and experimental tests,” Journal of Geophysical. Research,” Vol. 106, No.B1, pp.553-566 (2001).

13. Gray, J.M.N.T., M. Wieland, and K. Hutter, “Gravity driven free surface flow of granular avalanches over complex basal topography,” Proc. R. Soc. London, Ser. A, 455, pp.1841-1874 (1999).

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圓柱堆翻轉、變形破壞與流體化現象之輸送帶實驗分析

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