Using trenches to reduce tunnelling vibrations

Wave barriers are often used in engineering practice to reduce the ground vibrations induced by man-made sources such as traffic and machine foundations. In this paper, the results of a numerical study, with three-dimensional finite elements coupled with infinite elements, are presented to examine the effectiveness of open and backfilled trenches as wave barriers in reducing the ground surface vibrations due to tunnelling activities. The effects of the geometrical dimensions of the trenches and material properties of the backfill on the reduction of ground vibrations are studied. It is found that the percentage reduction in the vibration velocities increases with increasing depth of the trenches, and softer backfill materials yield a better screening effect than stiffer materials.