The cutting process in water saturated sand has been the subject of research in the dredging industry for decades already. The Dutch dredging industry started this research in the sixties, resulting in a number of models in the seventies and eighties (van Leussen & van Os (1987) and Miedema (1987 and later). The application of the theory in the offshore industry is rare, although Palmer (1999) used it. In the last decades trenching has been a practice where these theories can be applied and with the tendencies of working in deeper water and in arctic conditions it is useful to try to combine the knowledge from the dredging and the offshore industry regarding cutting processes. The cutting process in water saturated sand is dominated by the phenomenon of dilatancy. Due to shear stresses, the porosity of the sand increases, resulting in an absolute decrease of the pore water pressures. Since the soil stresses are a constant, and equal to the sum of the grain stresses and the pore water stresses, this implies that the grain stresses increase with decreasing pore water stresses. This results in much higher cutting forces. The decrease of the pore water stresses is limited by the water vapor pressure and so are the cutting forces. At shallow waters, the pore water may start to cavitate if the strain rates are high enough, but at very deep water this will probably not occur. In this paper the basics of the cutting theory are explained. This cutting theory however requires a lot of finite element calculations in order to determine the pore water pressures. The paper gives simplification that allows the user to apply the theory with the help of pre-calculated coefficients.
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