地震波作用下飽和砂土動態強度之研究

Abstract

本文採用宜蘭頭城砂為試驗用砂，以氣漏法製成相對密度35%、55% 及75%之試體，在有效圍壓 1kgf/cm^2下，以氣壓式中空扭剪三軸儀分別 施予 3個不同型態之震波，求取在雙振幅應變達 3%、5%及10%情況下，地 震波對動態強度之影響，並實際引用過去宜蘭地區發生液化之記錄與本試 驗值作一比較。 由試驗結果顯示：(1)不同波型將造成砂土動態強度 、孔隙水壓激發情形之差異 (2)地震波與均值波間有著一定的轉換關係 (3)在同一深度，以地震波評估砂土液化所需之地表加速度值，比相當之 均值波者為小 (4)加速度比與覆土應力比間具有線性函數之關係。 This project used Tou-Cheng sand as sand specimens which were made by air-pluvition method in three different relative densities, 35%, 55% and 75%. Effective confining pressure was kept as 1 kgf/cm^2 . The sand was tested with three seismic loading patterns by torsional shear apparatus and the liquefaction strengths were defined for 3%, 5% and 10% double amplitude shear strains in order to find the relationship between the dynamic strength and seismic loading pattern. Besides, the liquefaction strength will be compared with the test results recorded in Yee-Lan area. The test results show that：(1)different types of loading pattern applied on specimen result in various dynamic shear strength and behavior,(2)there is a transformable relationship between regular and seismic loading pattern, (3)the earthquake peak ground acceleration causing liquefaction assessed by seismic torsional shear tests will be smaller than that by the regular torsional shear tests at the same depth, (4)it was found that the acceleration ratio against stress ratio is a linear function.