飽和砂土動態強度之研究-台灣地區砂性土壤

Abstract

本文採用台灣地區之砂性土壤"福隆、里港、竹安砂"為試驗砂，以氣漏法 製成相對密度 30%、50%、75% 之試體，有效圍壓控制在1kg/cm2，分別以 反復動力三軸儀和中空扭剪三軸儀施以不同之反復荷重，比較各飽和砂土 在不同受剪型態下之動態強度、孔隙水壓激發情況及試體變形行為，並且 擷取另兩種台灣砂土"大安砂、大溫砂"與日本豐浦砂(Toyoura sand)之試 驗成果加以分析，並比較其異同點。試驗結果顯示：(1)不同之反復荷重 施加方式，均造成各砂土動態強度、孔隙水壓激發情況及變形行為有所差 異，動態強度之差異量會隨砂土種類有所不同，且以反復動力三軸試驗會 得較高之液化阻抗值。(2)藉由砂土之物理特性及動態強度行為，將本文 中使用之台灣地區砂性土壤歸類為三種，並經由體積減少潛能 Vd 與反復 應力比之關係，比較此三種砂土及與日本豐浦砂間動態強度行為之差異。 The project used three kinds of soil which are sampled from different areas of Taiwan , Fu Long, Li Gun and Chu Ain. The spe- -ciment of each kind of sands was made by air-pluvition method in three different relative densities,30%,50% and 75%. Effective confining pressure was kept as 1kg/cm2. All the sand was tested with regular loading by torsional shear apparantus and cyclic triaxial apparatus respectively in order to compare dyna- -mic shear strength, pore pressure buil-up, and deformation under different type of loading. Besides, the result of two diff- -erent kinds of sands in Taiwan, Da Ain and Da Wen, were adopted to analyze together. The test results show that:(1) Different type of loading applid on speciment results in different dynamic shear strength and behavior. The dynamic strngth obtained from cyclic triaxial test and torsional shear test varies as soil type is different, however cyclic triaxial test gets the large liquefaction resistance than torsional shear test does. (2) By the physical character and dynamic streng behavior, the analyzed Taiwan's sand can be divided into three categories, and via the relation between volume decrease potention Vd and cyclic stress ratio, we can see the different dynamic character between sands and Japanese Toyoura sand.