飽和度與細料含量對回填砂土之變形性及液化特性之探討

Abstract

本文以雲林麥寮水力回填砂為試驗材料，探討在振動力作用下，砂土的動態變形性質 ，藉以評估現地受地震力作用時，可能產生之沈陷量，今為考慮土層實際分佈狀態，以三 種不同飽和度之砂土S=100%､S=50%､S=0%；並以另外三個參數，細粒含量：0%､10%､20 %，相對密度：30%､50%､70%，及應力比：0.15､0.3､0.45､0.6，作為試驗控制條件， 使用動力三軸儀進行試驗，試驗結果顯示：(1) 飽和度對砂土之變形有明顯之影響，在飽 和度S=100% 有液化產生時變形量最大，乾砂次之，而飽和度S=50%時因受水分吸附作用影 響在低密度狀態下的變形量反較乾砂為小，但在高密度狀態下則略大於乾砂。(2) 細粒含 量依次為 0% ､10% ､20% 增加時，會使液化潛能增加，對體積變化量之影響比值約為 1：1.5：1.7。(3) 液化潛能和變形量與砂土之緊密程度有關，愈緊密者其對液化及變形 之阻抗均較大，依試驗所設定的三個相對密度 30%､50%､70%條件下，對體積變化之影響 成線性關係比值約為1：0.7：0.4(4) 振動力大小是對土壤液化及變形為最重要的一項影 響因素，從實驗結果顯示，變形量隨應力比成冪級數關係增加。(5) 在不飽和砂和乾砂狀 態中，N=10 的體積變化量約為N=30時的70%，可知大部份的體積變化發生在前十次的震動 週期中。 This thesis aims to investigate the dynamic deformability of sand under shaking by using Yuen-Lin Mai-Liao hydraulic-filled sand ,and predict the possible settlement in the field when it undergoes earthquake force. In order to match the real distribution of soil layer, this thesis prepares some soil specimens that have different conditions:(i) Degree of Saturation Sr=100%, 50% and 0% individually; (ii) The fine content =0% , 10% and 20% ;(iii) Relative Density Dr=30%,50% and 20%;(iv) Stress Ratio=0.15, 0.3, 0.45 and 0.6 . The specimens are subjected to dynamic triaxial test by using show the facts like below.1. The degree of saturation has great influence on the deformation of sands . When the degree of saturation Sr=100%, which occurred liquefaction, it got a maximum deformation , and dry sands got a deformation less than that described above . However , the sands with Sr= 50% get a less deformation than that of dry sands because of adsouption of water at low density situation. 2. The potential of liquefaction will increase in order of fines contents with 0%,10%,and 20%.And the ratio of influence of volume change is about 1:1.5:1.7. 3. The degree of density of sands is related to the potential liquefaction and deformation. The greater density of the sands, the more resistance to the liquefaction and deformation . For the three Dr= 30% , 50% , 70% set in the experiment , it gets a relationship to the influence of volume change, and the ratio is about 1 : 0.7 : 0.4 . 4. The most important influntial factor to the liquefaction and deformation of soils is the magnitude of Vibration force. The results of experiments show that the deformation increases with ratio of stress in a power series relation. 5. In the situation of unsaturated and dry sands, the magnitude of volume change at N=10 is about 70% of that N=30. Thus we knows that most volume change occur in the first 10 times of shaking periods.