Experimental and numerical investigations on buffer performance of geofoam subjected by the impact of falling rocks with respect to different shapes

Geofoam with good buffer performance and low density is proposed to replace part of the sand, forming a composite cushion to resist rockfall impact. On the other hand, falling rock is usually variable and irregular in shape. In this study, laboratory tests and numerical research are conducted to study the buffer performance of geofoam, as well as the effect of the rock shape. When the rock shape changes from the flat form to the cone form, more time is needed to undergo the impact process and the maximum impact force decreases. Thicker geofoam is advantageous for reducing the impact force. However, the decrease degree is affected by the rock shape. Both the geofoam thickness and the rock shape have an obvious effect on the maximum deformation and the vertical stress in the geofoam. Thicker geofoam can amplify the influence of the rock shape on the stress in the beam. Accordingly, in the design of an effective composite cushion in a rock-shed, the geofoam thickness necessarily requires appropriate determination to meet both the buffer performance and the cushion deformation. Furthermore, the rock shape plays a crucial role in evaluating the buffer performance of the composite cushion.