細粒料對粉土細砂小應變勁度之影響

Abstract

在過去的四十年間，室內試驗關於控制乾淨砂微小應變下土壤勁度衰減之行為的影響因子，已經有相當好的結果。然而，在自然界中，許多砂土都具有細粒料，但目前關於細粒料含量對砂土的影響，多著重於土壤抗液化強度之研究上。關於細粒料含量對於粉土細砂微小應變土壤勁度衰減行為影響之報告有限。本研究所使用的麥寮砂（MLS）為台灣西部地區典型砂土，具有相當高含量的粉土（silt）。根據過去試驗結果顯示，麥寮砂具有高壓縮性且膨脹性不高的特性。 本研究目的主要以不同麥寮砂細粒料含量進行往復式及單向式微小應變三軸試驗，並於三軸試驗設備中加入剪力波元件（Bender Element），以求得完整且連續之模數遞減曲線及阻尼比遞增曲線，以分析細粒料之影響。本論文中敘述研究之背景、目的、試驗程序與試驗結果資料，並對於粉土細砂中剪力模數衰減特性進行分析、討論並提供建議。

During the past four decades, laboratory studies on the modulus degradation of clean sands under small strain conditions have been plentiful. However, natural sands often contain various amounts of fines. Available reports on the behavior of silty sands are mostly related to the cyclic shear strength rather than stiffness of the material. This research concentrated on Mai Liao sand (MLS), which was a typical silty sand along the West Coast of Taiwan. MLS was relatively compressible and had a less tendency to dilate when sheared. A series of strain controlled cyclic and monotonic triaxial tests have been performed on MLS in this research. The triaxial cell was equipped with bender elements to measure shear wave velocities of the triaxial specimen. A complete modulus degradation curve was then established by combining the moduli values deduced from the shear wave velocities and cyclic triaxial compression tests. The thesis describes the background of the research, it’s objectives, research procedures of the small strain triaxial test. The test results were analyzed and the influence of silt contents on MLS were discussed.