利用模型試驗探討顆粒性土壤邊坡滑動之行為

Abstract

台灣山坡地每逢颱風暴雨，經常發生相當規模之山崩、地滑、土石流等災害，邊坡破壞滑動將對下方的建築物、交通要道及人民生命財產造成重大影響。由於邊坡破壞後滑動範圍之預測一直沒有定論，故本研究希望對於邊坡破壞後之運動行為及影響範圍有更深入的了解，以助災害之防治。 本研究欲探討顆粒性材料於邊坡破壞後之行為，利用一台室內物理模型--邊坡滑動機制試驗儀，以越南砂為試驗材料，模擬並觀察邊坡破壞之運動行為。同時以電荷耦合元件(Charge Coupled Device，CCD)配合模型進行攝影，擷取邊坡滑動過程中顆粒之運動影像，再進一步應用質點影像測速儀(Particle Image Velocimetry，PIV)進行影像分析，所使用的是PIVview2C/3C軟體，來處理質點數值向量化，以建立運動過程之位移軌跡及質點速度，了解乾砂之滑動機制。 由試驗結果可得知，影響顆粒性土壤邊坡滑動之相關參數為坡角(含上、下坡)、坡面材料、土壤之相對密度等，無論是由速度或影響範圍進行比較，皆有一致的影響結果。其中，當上/下坡坡度大、相對密度小、底層為填砂的情況之下，滑動速度與影響範圍會較大。 此外，藉由文獻的整理與回顧，以現階段各學者專家之研究成果為基礎，將目前邊坡滑動分析方法作整理，瞭解各種分析方法的限制條件、缺點與簡化條件，再應用顆粒力學與運動物理學之基礎，獲得邊坡滑移運動影響範圍之簡化型解析解，嘗試經由數學式來幫助了解土體在邊坡滑動之影響。

Slope instability resulting from erosion, landslides, debris flows, rock falls, and so on is a serious problem in Taiwan. These slope failures have caused tremendous impacts on economic and loss of lives. And until now, there have been no conclusions whatsoever in predicting the influence area after a slope fails. Thus, the aims of this study are, first, to understand the behavior of movement of granular soil slope and its corresponding influence area, and to derive an analytical solution of the said influence area. For the first objective, in order to study the mentioned behavior, a physical model composed of Vietnam sand was used to perform some tests. Experimental images were taken by charge coupled device (CCD) cameras and the dynamics of the velocity of sand was measured by particle image velocimetry (PIV) measurement technique. PIVview2C/3C software was used to deal with the images taken in all tests. And for the second objective, from the concepts of particle mechanics and kinematics, the simplified mathematical solution was derived. The results show that the relevant factors influencing the slope failure are the slope angle of lower slope, material in the base of slope, relative density, and slope angle of upper slope in order of influence degree. In views of velocity or of influence area, the order of influence degree is the same. In addition, both the sliding velocity and the influence area are larger if the slope angle is steeper, the relative density is smaller and using sand as the base material. Moreover, the findings in this study will be helpful to reduce the risk of loss of lives under the threat of slope failures.