摘要 凝聚性沉泥(淤泥)常在水庫、湖泊、出海口處形成淤積。民國93年8月，艾莉颱風造成石門水庫原水濁度過高，使桃園地區民生供水遭受重大危機。本研究將採用石門水庫淤泥樣本，以不同高度沈降管進行沈降實驗，並以簡易的測壓管進行壓力實驗，來量測其阻礙沈降至壓密的水頭高度變化，探討超額水壓的變化過程，最後將沈降、壓力實驗結果與前人實驗、理論之結果相互比較，期望能瞭解淤泥在沈降、壓密的過程中所呈獻的物理行為。 實驗結果顯示，重量濃度在8％以上屬於凝聚性沈降，且不同的濃度會有不同的沈降行為。在沈降過程中，當底部有沉泥沈積時，即開始有壓密的作用產生，使超額水壓轉化為有效應力。濃度在40％時有明顯的microventing情形發生，導致超額水壓先上升再消散。濃度20％、24％、30％壓密時的超額水壓消散情形與前人理論比較結果相符。 ABSTRACT Cohesive sediment usually deposits in reservoir, in lakes, and at estuary. The sampled mud in Shihmen Reseroir was used in this study with settling columns of different heights to perform settling measurement. Pore pressure measurements were conducted to examine the relaxation process of excessive pore pressure. The results of the settling and pressure measurement were compared with the consolidation experiments and theories of Been and Sill. When the weight concentration of mud is above 8%, it belongs to cohesive settling. Further, different concentrations have distinct effects on settlings. When the concentration of mud reaches 40%, the significant microventing causes the excess pore pressure to rise at first then dissipate later. While the concentration is between 20%-30%, the dissipations of excessive pore pressure agrees with the consolidation theories of Been and Sills.