ABSTRACT: In the trailing suction dredging, the mechanical ploughing method is mainly used to loosen the hard sediment on the seabed. Cutter teeth are the structures which are used to loosen material from the seabed. The interaction between seabed soil and structure is an important issue in geotechnical engineering as well as coastal engineering. It is necessary to study the pore water pressure changes on the tooth-soil interface when subjected to mechanical ploughing, so as to study the required drag force exerted on the cutter teeth. The experiments were conducted in this paper to study the variation trend of pore water pressure in the soil while the cutter tooth moving forward at a specified speed. The experimental results show that the pore water pressure was decreased to be negative, even close to be a complete vacuum, while the seabed soil was subjected to a complex load of squeezing, raising and crushing.