本研究使用之矽溶膠灌漿液具耐久性和良好砂土灌注能力，雖具強鹼性(pH = 10)，但膠凝後，膠體性質穩定。依本研究針對矽溶膠灌漿液之膠凝行為和膠凝後之強度性質試驗發現: 矽溶膠體強度隨二氧化矽和促凝劑濃度之增加而增加；在相同膠凝時間下，隨二氧化矽濃度增加，所需之促凝劑濃度會減少。此外，膠體強度和膠凝時間，也受溫度與砂土表面吸附粉末性質影響。雖然膠體強度不高，但因不具流動性，一旦充填砂土孔隙後，即足以防治土壤液化發生。在不同的灌漿砂試體準備方式下，因矽溶膠在砂土孔隙中分佈方式不同，會影響灌漿砂之強度和透水性質。其中，以攪拌方式準備之試體，因砂土顆粒接觸點間裹有漿液，所以其強度較以低壓灌注、而砂土顆粒接觸點間未有漿液之試體，高出約0 ~ 15%，兩者之差距隨膠體強度之增加而增加。比較以1.5倍和3倍砂土孔隙體積灌漿量注入之灌漿砂試體時，雖前者有少量氣泡存在孔隙間，但兩者之抗壓強度和透水性差距不大。雖前者較具經濟性，但若考量地層和地下水文之變異性，仍建議以3倍孔隙體積灌漿量進行抗液化土壤改作業為宜。

Colloidal silica grout was used in this study due to its good durability and injectability to sand. Although its pH value is high (=10), its gel is stable and has good durability under the groundwater table. Having done a series of laboratory tests on colloidal silica and its grouted sand, the findings can be presented as follows. The strength of colloidal silica grout increased with the concentration of silica and reagent in the grout. Under the same gel time, the higher the silica concentration in the grout, the lower the concentration of reagent is required. In addition, the strength and gel time of colloidal silica grout are also affected by the temperature and the adsorbed powder materials on the surface of sand particles. Although the strength of colloidal silica grout is not high, it is still capable to prevent the soil liquefaction from happening because of the non-liquid nature of the gel. Once it fully or partial fills the porosity of sand, sand will not be able to liquefy during earthquake. Furthermore, the properties of grouted sand are affected by the preparation methods of grouted sand. For example, the grouted sand specimens prepared by stirring mix method, the contact points between sand particles are coated with a thin layer of grout and bound the particles together. So a higher strength was obtained compared to those prepared by injection method which yields no grout coating at the particle contact points. The former shows a 0 ~ 15% higher strength than the latter. The difference in strength increases with increasing grout strength. Comparing the grouted sands prepared with 1.5 times and 3 times the porosity volume grout injection, there is some air bubbles in the pores of sand for the former. But the difference in the compressive strength and permeability between these two is not obvious. Finally, 1.5 times the porosity volume grout injection may seems to be more economic. But considering the changing nature of subsoil and groundwater conditions, it is still suggested that 3 times the porosity volume grout injection is more accountable for ground improvement against soil liquefaction.

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