Definition of Fines and Liquefaction Resistance of Maoluo River Soil

本研究取南投市貓羅溪岸出現液化現象之工務所與第二條高速公路高架橋下附近土壤， 分別以200 號篩與400 號篩作為細粒料之界定標準，藉由控制試體乾密度相同，改變試體中 之細粒料含量，利用C.K.C.動力三軸儀以及中空圓柱試體扭剪儀進行動力試驗，求得不同細 粒料含量土壤之抗液化強度，以便探討不同細粒料界定標準與特性對土壤抗液化強度之影 響。根據動力試驗結果顯示，不論其細料之界定為何，當細料含量不超過30 %時，土壤整體 的行為偏向與一般砂性土壤的行為相似，呈現較小的變形性、剪力模數維持定值以及孔隙水 壓力在破壞前出現激增等現象，而對純細粒料試體，會出現變形量大、剪力模數隨反覆作用 次數增多而改變等動態特性。當土壤處於疏鬆狀態之條件下，具相同乾密度之試體，其抗液 化強度會隨著細粒料含量的增加，出現先下降後上升的趨勢，土壤在細粒料含量約為20-30% 時出現最小的液化阻抗強度。純細粒料試體抗液化強度約為此最小抗液化強度的1.28 至1.45 根據本研究中之試驗結果與他人之研究結果相比較，可以發現貓羅溪岸土壤在疏鬆狀態 下，以400 號篩作為細粒料界定標準時，其細料含量對抗液化強度之影響，比以200 號篩為 界定標準更顯著，而且所得細料含量與液化強度關係較有一致性。Two definitions of fines, soil particles finer than the No. 200 sieve (0.075 mm) and No. 400 sieve (0.038 mm), are adopted to evaluate the effect of fines content on the liquefaction resistance of the silty soil in the Maoluo River area of Nantou City. The specimens of different fines contents according to these two definitions of fines were prepared by moist tamping to a dry density of 1400 kg/m3. The liquefaction resistance of these specimens were tested using the cyclic triaxial test apparatus and the cyclic torsional shear device. Comparisons were made between the liquefaction resistances of soils containing fines according to different definitions. The results show that the effect of fines on the liquefaction resistance of Maoluo River soil is more pronounced and consistent based on the fines content defined as the portion finer than the No. 400 sieve than that with fines defined as soil passing the No. 200 sieve