During the construction of the LYG-302-H1.1 section of the phase Ⅱdredging projcet of the 300,000 tons waterway in Lianyungang Port,pipe clogging frequently occurs in cutter-suction dredgers,which seriously affects the construction efficiency.To avoid the frequent occurrence of this accident,we analyze the characteristics of soil layers and the reasons of pipe clogging by collating the soil data in the accident prone area,and summarize the soil quality index of such difficult excavation areas.The results show that the soil layer in this kind of area is not uniformly distributed.The clay layer contains clayey silt and sandy silt at the same elevation,and exists some calcareous cementation in the clay layer.The number of standard penetration is greater than 20.