THE BULLDOZER EFFECT WHEN CUTTING WATER SATURATED SAND

In the last decennia a lot of research has been carried out into the cutting of water saturated sand at small cutting angles, especially at the Delft University and Deltares. Because of tunnel boring machines there was also interest in larger cutting angles in the 90's. Now this can also be applied to the bulldozer effect in front of drag heads or the dragging of ice keels resulting in soil displacements under gouges. At small cutting angles the sand will flow over the blade according to the flow type of cutting mechanism, however at large angles a wedge will occur in front of the blade, while at very large cutting angles the sand will be pushed under the blade. Based on FEM calculations of the pore pressures a method has been developed named the parallel resistor method, in order to determine the pore pressures in the water saturated sand. Once these pore pressures are known, the forces and moments can be determined and it can be predicted at which cutting angle a static wedge will start to occur and at which cutting angle the sand will start to move under the blade resulting in much larger soil deformations. The paper will describe the model and also give a recipe on how to determine when the static wedge will occur.