本研究以峴港砂代表現地回填料，進行砂土液化性質及水泥改良效果之評估。在不同水泥配比與養治時間之條件下對含細料砂質改良土之力學性質作一探討。本研究之實驗重點乃以相對密度為40%之砂土並製作不同細料含量5%、10%、15%，配以0.5%、1.0%及2.0%的水泥配比，利用濕搗法製作改良土試體，經7天或28天養治後，進行無圍壓縮試驗及動力三軸試驗。 經由試驗結果發現，添加水泥於含細料砂質土壤內並加以混合攪拌，對於剪力強度的提供有著明顯的效果。水泥改良土之無圍壓縮強度隨著水泥配比及養治時間之增加而顯著的提高；另一方面，隨著細料含量之增加，剪力強度亦有相同提高之趨勢，但細料含量大於10%後，因結構之改變造成無圍壓縮強度有下降之趨勢。 在本研究的試驗條件下，含細料砂質土壤之液化阻抗較高於未含細料之砂土；而經水泥改良後之含細料砂土，又遠高於含細料之砂土。養治時間為7天時，添加2%水泥配比含細料砂土之液化阻抗將因而提升。養治時間28天時，含細料砂土添加1%水泥後，其液化阻抗即可獲得明顯的改善。而控制細料含量於10%左右添加水泥進行改良，即可得到良好之成效。另外，本研究亦探討了水泥改良土之剪力模數、剪應變與水泥配比間的關係。經試驗及分析後，發現改良土對以上諸特性均有良好之改良效果。且在相同之應力振幅作用下，添加水泥並控制細料含量為10%左右時，可使產生之剪應變較其他配比之改良土為小。 This research used Danang sand as the representing material of in-situ reclaimed soil to investigate the properties of liquefaction and to evaluate the improvement effects attributed to using cement. A series of experiments have been done on a set of samples made by using wet tamping method. The set consists of samples having different fine contents (5%, 10%, and 15%) mixed with different cement contents (0.5%, 1.0%, and 2.0%). After curing for 7 or 28 days, the unconfined compression tests and dynamic triaxial tests were conducted. According to the experimental results, adding cement into the sands containing fine contents will significantly be enhanced the unconfined compression strength. On the other hand, the shear strength tends to be improved while the fine content is increased. However, when the fine content goes up to more than 10%, the unconfined compression strengths tend to decrease due to the change of soil structure. Under the experiment conditions, when the curing period is 7 days, adding cement of 2% mixing rates to the sand containing fine content will increase the liquefaction resistance. For the case of 28-day curing, adding cement of 1% mixing rates to the sand containing fine content will also have the same effect. As a brief summary, by controlling the fine content at about 10% along with adding cement, it will result in a better liquefaction resistance than the other ratio.
