含海水鹽性改良砂土之力學特性

陳彥奇(Yan-Chi Chen)

指導教授 ： 張惠文

國立中央大學/工學院/土木工程學系/碩士(2006年)

摘要

摘要

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人工海水為拌和水及養治水，相對密度為40%之砂土並製作不同細料含量5%、10%、15%及20%，配以0.5%、0.7%、1.0%及2.0%的水泥配比，改良材料選用波特蘭水泥第I型及第V型，養治時間有7天、28天、56天或120天，再利用濕搗法製作改良土試體，進行無圍壓縮試驗及動力三軸試驗。
經由試驗結果發現，隨著細料含量之增加，剪力強度有提高之趨勢，但細料含量大於10%後，因砂土結構之改變，造成無圍壓縮強度有下降之趨勢。而改良砂土之鹽度愈高，其無圍壓縮強度有明顯降低之趨勢。
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。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。控制細料含量於15%左右添加水泥進行改良，即可得到良好之成效。而鹽度的增加與液化阻抗的高低明顯成反比。另外，本研究亦探討了水泥改良土於反覆加載15次時之剪力模數、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15%左右時，可使產生之剪應變較其他配比之改良土為小。

關鍵字

細料含量 ； 養治時間 ； 水泥配比 ； 鹽度 ； 液化阻抗

並列摘要

ABSTRACT

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 (0%, 5%, 10%, 15% and 20%) mixed with different cement contents (0.5%, 0.7%, 1.0%, and 2.0%). After curing for 7, 28, 56 and 120 days, the unconfined compression tests and dynamic triaxial tests were conducted.
According to the experimental results, 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. Otherwise, the unconfined compression strengths tend to decrease substantially with the increasing of salinity.
Under the conditions of experiments, the liquefaction resistances of treated sands with the 15% fine content are stronger than the liquefaction resistances of treated sands with the other ratio of fine content. When the curing period is 7 days, the liquefaction resistances of treated sands with the fines will increase obviously due to adding 2% of cement mixing rates. For the case of 28 days curing period, the liquefaction resistances of treated sands with the fines will also have the same effect after adding 1% of cement mixing rates. As the increasing of salinity, the liquefaction resistances of treated sands with the fines decrease continuously. On the other hand, the result of this research shows that the cement material will be contributive to improve the dynamic properties of sands such as shear modulus and shear strain.

並列關鍵字

liquefaction resistance ； salinity ； fine content ； cement mixing rate ； curing period

參考文獻

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