ROCKPATH程式剛體版之試驗驗證與應用

Test Verification and Application of the Rigid-body Version of ROCKPATH Program

李濬易(Chin-Yi Lee)

指導教授 ： 葛德治 ； 馮道偉

中原大學/工學院/土木工程研究所/碩士(2002年)

https://doi.org/10.6840/cycu200200164

摘要

於山多及豪雨地震頻仍之地如台灣，落石 (rock-fall) 對於山區道路、房舍及水力設施的維護上一直屬於一個棘手問題。攔石牆及防護網等為減低落石災害最常見之被動工法，然而設計這些防護結構首先需推估現地落石之運動軌跡及彈跳高度。落石之運動軌跡及彈跳高度現今通常由實驗方法及計算模式來估計。
國內葛德治所發展之單粒落石運動模擬程式剛體版「ROCKPATH」為本論文主要之分析工具，一系列的室內模型試驗及國內兩個現地案例分析將用來驗證該程式之適用性與準確性。藉著自行撰寫之正弦坡形生成程式 (波長l，振幅A)，一段近乎水平坡面之規則起伏對於一個落石 (落石直徑D) 之彈跳行為也將進行參數研究。
在室內模型試驗方面，「ROCKPATH」程式所得之落石軌跡與模型試驗所量測者十分接近；而於案例分析中給定同樣輸入參數下，該程式所模擬者也與現地觀測及CRSP 程式之分析結果幾乎相同，因此「ROCKPATH」程式之適用性與準確性得以驗證。至於上述參數研究方面，以落石第一次與第二次觸地點之水平距離 L1 來比較可知：1) 當每個坡形擷取點數 N＞16、波長對波幅比 λ/A＜5 且落石直徑對波幅比 D/A＞5或λ/D＞5且A＜1m時，落石之彈跳行為已變化有限；2) 於 λ＞20m 時，回彈係數 (en, et) 之影響也不大。
為了更真實補捉單粒落石之運動行為，「ROCKPATH」程式剛體版之未來發展有落石及坡面接觸特性資料庫之建立、實際曲線坡形及空氣阻尼之考慮、三維圓球單粒落石模擬程式之建構等。至於多角狀落石及落石群之效應探討，則需藉助不連續計算程式方可完成。

關鍵字

室內模型試驗 ； 運動軌跡 ； 「ROCKPATH」程式剛體版 ； 接觸特性 ； 回彈係數 ； 落石

並列摘要

In a mountainous region with heavy rainfall and intensive earthquakes like Taiwan, rock-fall is a very troublesome issue for maintaining roads, buildings and hydraulic facility near the valley sides. Rock catch walls, protection fences and nets are common passive remedies for reducing such a hazard. It is obvious that the knowledge about the motion behavior of falling rocks, such as moving paths, velocities and bouncing heights, is essential for the design of these protection structures. The moving paths of falling rocks have recently been estimated by experimental approaches and computational models.
A motion simulation program for a single falling rock, ROCKPATH, locally developed by Ke with the rigid-body capability is the main research tool in this thesis. A series of laboratory model tests and two local case studies were performed to examine the suitability and accuracy of this program. With the aid of a sine wave profile generator (wavelength l and amplitude A), a sensitivity study of the bouncing behavior of a rock (diameter D) on a quasi-horizontal plane with regular roughness was also conducted.
For the laboratory tests of one rock falling on several different slope materials, ROCKPATH code yielded the moving paths fairly comparable to those of test observations. Given the same input parameters, ROCKPATH code also reproduced the simulation results similar to those investigated by previous researchers in the two field cases. Therefore, these outcomes definitely assure the adequacy and precision of ROCKPATH code. According to the results of the above sensitivity study by using the horizontal distance between the first and second impact points L1 as a comparison index, it can be concluded that: 1) when the number of dividing points per wave N>16, wavelength-amplitude ratio (l/A)<5 and rock diameter-amplitude ratio (D/A)>5, l/A>5 and A<1m, the bouncing behavior of the target rock varies less afterward; 2) the effect of (en, et) is not remarkable for l>20m.
In order to more precisely capture the falling behavior of a single rock, the future developments of ROCKPATH code may be composed of establishing a database of rock-slope contact properties, performing more model tests, considering real curvilinear slope profile, surface damping effect and three-dimensional problems with a spherical falling rock. On the other hands, the complex problems of multiple and polygon-shaped falling rocks may be handled through the discontinuous computational codes.

並列關鍵字

contact property. ； restitution coefficient ； rigid-body version of ROCKPATH ； laboratory model tests ； rockfall ； moving path

參考文獻

[2] 林育玄 (2002)：「坡面回彈係數及粗糙性於單粒落石運動軌跡之影響」，碩士論文，私立中原大學土木工程研究所，中壢。

[7] 紀宗吉、陳宏宇 (1997)：「落石運動軌跡之現地調查與模擬分析案例介紹」，地工技術，第64期，第59-68頁。

[20] Azzoni, A. and de Freitas, M. H. (1995), "Experimentally Gained Parameters, Decisive for Rock Fall Analysis," Rock Mech. & Rock Engrg., Vol.28, NO.2, pp.111~124.

[21] Evans, S. G. and Hunor, O. (1993), "The Assessment of Rockfall Hazard at the Base of Talus Slopes," Can. Geotech. J. Vol. 30, pp.620-636.

[24] Ke, T. C., & Bray, J. (1995), "Modeling of Particulate Media Using Discontinuous Deformation Analysis," Journal of Engineering Mechanics, pp.1234-1243.