囿於環保與用地問題，目前火力發電廠已有在鬆軟之水力回填煤灰場址構築重型儲煤堆或擴廠之規劃。但對於以水力回填煤灰造地所形成高含水量、高孔隙比與低強度地盤之工程性質研究，則甚為缺乏。究其原因，實為過去從未有在煤灰填築場址上，建造重型結構物之想法。然而，在如此鬆軟之地基如何安全承載重型結構物載重與地震力的作用，實為工程設計應審慎考慮之問題。因此，本研究特針對水力回填造地後之現地煤灰的動態特性進行研究，期能對此類場址之地基耐震設計有所幫助。 本研究規劃一序列現場試驗、取樣以及各種室內物理、化學性質試驗，求得現地煤灰之物理指數性質與現地工程性質。並對不同取樣方式所得試體與重模試體進行大量之三軸動態強度試驗，求得各種煤灰試體之液化強度曲線與超額孔隙水壓激發特性。 研究結果顯示，現地煤灰之土壤動態強度較一般液化地區的砂土為高；煤灰土層的動態強度隨著粗顆粒爐底灰含量的增加而降低；經擠壓砂樁改良過之煤灰土層，其液化強度有明顯的增加；粗顆粒煤灰受剪液化後，會產生顆粒破碎的情形；煤灰土壤受動態反覆應力作用時，其超額孔隙水壓比上升曲線分佈在一窄小的帶寬內；煤灰土壤受震液化後，其再壓密之體積應變量約為1％，較一般砂土為低；隨著煤灰所承受之最大剪應變增加，試體的再壓密體積應變量越大。 In this paper, a series of in-situ explorations and samplings were carried out in a coal ash deposit at central Taiwan. The deposit was formed with coal ash, a surplus of thermal power plant, by hydraulic filling. Laboratory physical, chemical and cyclic triaxial tests were then conducted to obtain the basic properties of the coal ash and its cyclic resistance. The in-situ explorations included the standard penetration test, seismic cone penetration test and cross- hole seismic survey. The in-situ samplings consisted of tube sampling during boring and block sampling in a pit. Test samples comprised undisturbed samples and remolded samples. It was found that the in-situ coal ash is a high void ratio, high water content, high fines content, low unit weight, low specific gravity, non-plastic, cohesionless, spherical shaped, granular soil. Although the in-situ coal ash is soft and non-plastic, its cyclic resistance is significantly higher than those of the hydraulic filled sandy soils in the same general area. This may be attributed to its high fines content and fine-grained size. Besides, the influences of many factors on the cyclic resistance of the coal ash were summarized, and the characteristics of excess pore pressure generation and re-consolidation after liquefaction were also presented. These test data may provide a valuable base for aseismic design in a foundation soil with coal ash.