在水平面上的顆粒物質崩塌過程之內部結構探討

本研究以實驗方式去探討顆粒在二維模型崩落情況的現象，並透過高速攝影機量測分析顆粒材料在瞬間幾何模型的崩落下所分佈的狀態，藉以了解對顆粒更進一步的研究。實驗採用五種不同顆粒材質做研究，分別是標準砂20-30、標準砂30-50、越南砂、玻璃珠1mm及2mm，並設計一系列高寬比比例(a=Hi/Wi)，來看出最後崩落的形態。然而由實驗結果得知，每種顆粒材質在隨著比例的不同，最終崩落表面都會出現不同的幾何形態，當比例小於某一臨界值則形態會呈現斜截狀幾何型態；反之，大於某一臨界值則會呈現錐形形態幾何型態，並且隨著不同的顆粒材質所得到最初比例的臨界值皆不同。此外，顆粒崩落表面的形態已由實驗結果得知，但本研究卻不知道內部情況的幾何，因此把整體顆粒砂堆一開始靜止照片與整體顆粒砂堆完全崩落後的照片，最後利用MATLAB程式分別把兩張照片的值做相互相減最終發現，當高寬比比例低過某一值時，則內部最後會呈現鐘型形態；反之，超過某一比例值時，內部則會呈現三角形幾何形態。

關鍵字

摩擦角；安息角

並列摘要

This research is an experimental study on the collapse phenomenon of two dimensional granular heaps. The flows are captured by a high speed camera and analyzed by image techniques. Five different kinds of granular materials are used in the experiments. They are the standard sand Ottawa sand 20-30 and 30-50, Shankan sand and glass beads of 1㎜ and 2㎜ in diameters. For each material, the same series of measurements are conducted. They are piled two-dimensionally into a series of heaps at different initial height-width ratios, a=Hi/Wi, and set to collapse flow by rapid releasing of lateral confining walls. The resulting heaps exhibit two distinguishing appearances: the Mexican-hat shape and the triangular-like shape. There exist critical values of a=Hi/Wi for each materials, which divides the final deposit appearance among the tow. Also by using image process techniques, e. q. image substraction, we are able to identify areas which remain rest through the transient motion. Interestingly, these areas also exhibit two distinguish appearances: the bell shape and the equilateral shape and are controlled also by a=Hi/Wi.