本研究以峴港砂代表現地回填料，進行砂土液化特性與水泥改良效果之評估。在不同水泥配比、養治時間及試體準備方式之條件下對改良砂土力學性質作一探討。本研究之實驗重點乃以相對密度為40%之砂土添加細料含量10%，配以0.3%、0.5%、1.0%及2.0%的水泥配比，利用濕搗法製作改良砂土試體。製作試體時所使用之拌和水有蒸餾水與人工海水兩種，本研究在配製人工海水時所需的鹽度定為35‰，用以模擬海洋環境。改良砂土試體經3天、7天、28天及56天養治後，進行無圍壓縮試驗及動力三軸試驗。 經由無圍壓縮試驗結果發現，氯離子會提高水泥的早期強度。養治天數28天以前，在相同配比、相同養治天數下，以人工海水拌和的試體強度會比以蒸餾水拌和的試體高。但當養治天數為56天時，以人工海水拌和的試體強度會較養治天數為28天時來得低，此結果與用蒸餾水拌和的試體恰好相反。 經由動力三軸試驗結果發現，改良砂土養治時間為7天時，添加水泥配比為2%時，試體之液化阻抗會提高，當養治時間為28天時，添加水泥配比為1%，液化阻抗便會增加，使試體較不易發生破壞。此外，本研究亦探討了水泥改良砂土之剪力模數、剪應變與水泥配比間的關係。經試驗及分析後，發現添加水泥改良後，以上諸特性均有良好之改良效果。 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 Danang sand for relative density (40%) and fine contents (10%) mixed with different cement contents (0.3%, 0.5%, 1.0%, and 2.0%). This research having two different blend water for making up samples, distilled water and artificial seawater. The degree of salt for this research is 35‰ which making up artificial seawater we need. After curing for 3, 7, 28 or 56 days, the unconfined compression tests and dynamic triaxial tests were conducted. According to the results of unconfined compression tests, it is understood that chlorine ion will improve the strength of cement treated sand. Before 28-day curing, the strength of samples mixed with artificial seawater are higher than that of the samples mixed with distilled water. But when curing period is 56 days, the strength will be a little lower for samples mixed with artificial seawater. This result is opposite to that of the samples mixed with distilled water. According to the results of dynamic triaxial tests, when the curing period is 7 days, adding cement of 2% mixing rates to the sand will improve the liquefaction resistance. For the case of 28-day curing, adding cement of 1% mixing rates to the sand will also have the same effect.
