本研究旨在利用K0中空扭剪試驗探討細粒料含量對飽和砂土孔隙水壓激發行為之影響，並建立可同時反映剪應變振幅、循環次數與細粒料含量之多維度模型。研究以渥太華砂為母材，並摻配取自麥寮砂之細粒料製備不同細粒料含量之試體（0%、7.5%、15%、35%、100%），於不排水、定剪應變反覆扭剪條件下量測超額孔隙水壓比(ru)累積之時程與循環演化。實驗結果顯示，當細粒料含量小於過渡細粒料含量時，砂顆粒形成主要骨架，孔隙水壓激發速度較快，且超額孔隙水壓比也較高；然而於細粒料含量大於過渡細粒料含量時，細粒料主導顆粒架構，孔隙水壓累積趨緩，所引致之超額孔隙水壓比較低，顯示細粒料所構成之骨架特性完全不同於砂土，可由此結果將試體分類為類砂土型(Sand-like)試體及類粉土型(Silt-like)試體。由遲滯迴圈觀察可知，儘管類砂土型試體及類粉土型試體在試驗結束時不一定有達到初始液化之條件(ru > 0.9)，但在循環次數足夠之情形下，於試驗結束時其剪力模數均落於100 kPa至200 kPa之區間，顯示初始液化條件無法完全表達試體剪力強度之折減。本研究依據各細粒料含量之試體所得資料繪製孔隙水壓激發曲面，進而建立多變數擬合模型，以細粒料含量(FC)、剪應變振幅(γ)、循環次數(N)與孔隙水壓比(ru)為主要控制變數，其中FC透過線性修正後使計算過程更為簡單、直觀，有效提升模型之使用性。研究結果顯示，擬合模型可合理描述不同細粒料含量下之孔隙水壓激發趨勢，並提供具物理意義之工程化參數，可作為含細粒料砂土之液化潛勢評估依據。

This study examines the influence of fines content on excess pore water pressure generation in saturated sands using a K₀-consolidated hollow cylinder torsional shear apparatus. Ottawa sand was used as the base material, with fines from Mai-Liao sand mixed to prepare specimens containing 7.5%, 15%, 35%, and 100% fines. Undrained cyclic torsional shear tests were conducted under constant shear strain amplitudes, and the excess pore water pressure ratio (ru) was continuously recorded. Results show that when fines content is lower than the transitional fines content, the soil behavior is governed by sand particle skeleton, resulting in rapid pore water pressure buildup and higher ru values. When fines content exceeds this threshold, a fines-dominated skeleton forms, leading to slower pore pressure accumulation and lower ru. These responses allow classification of the tested soils as sand-like or silt-like materials. Hysteresis loop analysis indicates that although initial liquefaction (ru > 0.9) is not always achieved, the shear modulus of both material types converges to approximately 100–200 kPa at large loading cycles, suggesting that liquefaction criteria based solely on ru may not adequately represent stiffness degradation. Based on the test results, pore water pressure generation surfaces were established and a multivariable regression model incorporating fines content, shear strain amplitude, number of cycles, and ru was developed. A linear correction to the fines content term improves model simplicity and applicability for liquefaction assessment of sands containing fines.

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