Abstract: Infinite element is an effective artificial boundary, which can be utilised to address the elastic wave propagation problem. Based on the traditional dynamic infinite elements, we proposed a novel dynamic infinite element using a directional interpolation technique. The shape function of the element has been derived in detail. The totally analytical stiffness matrix related to the element is developed to improve the computation effectiveness. By using the infinite element mentioned above, Lamb problem with line source in an elastic medium is computed. The validity of the infinite element is verified by comparing the computed results with the analytical solution of displacements on the ground. The example analysis shows that the edge size in the finite element mesh should be less than 1/8 shear wavelength. The distance between an imposed source point and the mesh boundary should be equal to 5 times the shear wavelength. The amplitude attenuation coefficient in the infinite element has little effect on the calculation results, and thus a relatively small value is recommended.

Key words: infinite elements, directional interpolation, elastic medium