煤灰具有比重輕、密度小、吸水率強、顆粒易破碎等特性，極易在地震中液化，而且水力排放之煤灰塘材料性質變異性大，因此欲有效利用此回填煤灰塘新建工程設施，有必要就其工程性質進行改良。鑑於日本311地震發生時，海埔新生地發生多處地層液化情形，但採用格狀改良處理之神戶市東方飯店並未因此受損害，故本研究使用二維數值模擬軟體FLAC 5.0 (Itasca)，對格狀改良後煤灰層的抗液化能力加以模擬研析。探討格狀改良工法之設計參數，包括格狀改良壁體之幾何參數和配置(如：厚度、深度、淨間距等)，對煤灰塘抵抗液化、震陷及側向位移能力之影響評估，並建立相關圖表，作為日後於煤灰塘上施作格狀改良時之初步設計參考。

Coal ash consists of low density, high water-absorbing, and crushable particles. Its engineering property is different from ordinary granular soil. To use the reclaimed land by coal ash as the construction site of new structures, it needs to improve the engineering property of coal ash. According to the previous research results, the grid type ground improvement method has shown its advantages in operation, efficiency, and quality compared to the sand compaction pile method. However, the topics studied in the previous research are limited to mixing ratio of binding agents, feasibility, materials, and preliminary design concept. No attempt was made to apply this method to practice because no research has been done to find out the relationship between design parameters and anti-liquefaction ability. To ensure the safety of future facilities founded on coal ash, a finite difference method and an effective stress method were used to analyze the liquefaction resistance of grid-type ground improvement in coal ash pond. In this paper, not only the property of coal ash is studied but also the geometry of grid-type improvement are discussed. This study offers a design principle for the panel wall of grid-type improvement. The cost breakdown for the pile foundation installed in grid-type ground improvement and in the sand compaction piles method is provided for the reference of designer.

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