高放性廢料處置之緩衝材料係由皂土或碎石(矽砂)-皂土混合材料構成。由於緩衝材料塊體之品質對於工程障壁之成效影響相當大，故壓製品質穩定之緩衝材料塊體為重要之課題。由於單軸壓實法壓製緩衝材料塊體具有成本低、省時及形狀精確之優點，故目前各國主要以單軸壓實法壓製緩衝材料。但由皂土壓製為高密度塊體過程中材料與模具間會產生壁面摩擦力，單純的施加壓實應力與密度之關係並無法真正表現粉體之壓實特性。 本研究以壁面摩擦力量測試驗討論壁面摩擦力及脫模力與壓實行為之關係。本研究首先改良傳統壁面摩擦力量測方法，並提出無壁面摩擦力壓縮曲線之概念，發展出以壓實應力平均法(包含積分平均法、幾何平均法及算術平均法)及長徑比外插法求取無壁面摩擦力壓縮曲線之方法。進而根據壁面摩擦力分佈理論推求最大脫模力與壁面摩擦力之關係，有效預測最大脫模力及脫模曲線之行為。 最後本研究依據微觀力學之觀念，建立一套碎石-皂土混合物壓縮曲線預測方法。僅需針對純皂土進行壓實試驗，即可預測不同碎石添加含量之碎石-皂土混合物壓縮曲線。如此可大幅減少實驗數量，並適用於壓縮曲線之加壓及解壓回彈過程，合理估算壓實應力、壓實密度及回彈量。將碎石-皂土之試驗結果與模式預測比較，證實在實用之範圍內預測結果相當理想。由於大部分國家之緩衝材料皆以多種配比設計考量，故當不同皂土、不同碎石顆粒材料選用時，透過本研究所發展之壓縮曲線預測方法，可快速掌握該設計緩衝材料之壓實行為及相關力學參數。 The buffer material in nuclear waste disposal was made up with pure bentonite or sand-bentonite mixture. The uniaxial compaction is time-saving and produce blocks with high precession in geometry. It is not necessary to reshape the geometry of block after compaction. The uniaxial compaction technique is widely used in buffer material researches. The major disadvantage of uniaxial compaction is that the blocks may become stress (or density) inhomogeneous due to the wall friction between block and the die. This study presents friction eliminate methods to correct friction effect and obtain friction-free compressibility curve. A series compaction test of varies h/d ratio and die wall condition were carried out in this study, and to demonstrate the method obtained friction-free compressibility curve of bentonite block. In accordance with micromechanics, sand-bentonite mixtue can be seen as the two phase composite material. Basis on this concept can predicted compaction curve and rebounded constrained modulus of sand-bentonite composite.
