Dilated polyhedra based discrete element method and its application of ice load on cylindrical pile

With the polyhedron elements with complex geometric shapes, the linear contact force model cannot precisely obtain the contact force and its direction and the contact deformation under various contact patterns. Due that dilated polyhedral element can be generated with superposing one dilating sphere on the surface of one basic polyhedron in the Minkowski sum theory to construct the geometric shape of irregular particle accurately, and then its contact detection between particles can be calculated easily, considering different contact patterns between vertices, edges and planes of the dilated polyhedral elements, a unified nonlinear viscoelastic contact force model is developed. In this model, the equivalent radius of curvature is introduced to calculate the elastic contact stiffness in normal direction. Meanwhile, the viscous force and the elastic force in tangential direction are simplified based on the contact force model of spherical element. To simulate the sea ice floes in broken ice region, the sea ice elements are generated randomly with the Voronoi tessellation algorithm. The ice loads on a vertical cylinder pile are simulated with the dilated polyhedral elements considering the buoyancy and drag forces of current. Moreover, the influences of ice velocity and ice floe size on the ice of pile are determined, and the distribution of ice load around the cylindrical pile is obtained. Finally, the limitation of the present dilated polyhedral element and its further modification are discussed. © 2015, Editorial Office of Chinese Journal of Theoretical and Applied Mechanics. All right reserved.