Experimental study on the multi-impact resistance of a composite cushion composed of sand and geofoam

Abstract

In the case of the rockfall hazards, multiple rockfall impacts usually occur. To improve the ductility and the multi-impact resistance ability of the rock-shed, geofoam is proposed to replace part of sand, forming a composite cushion. Two types of geofoam are selected in the paper, namely, expandable polyethylene (EPE) and expanded polystyrene (EPS). A systematic experimental study was conducted to compare the properties of EPE and EPS. The compression tests showed that EPE geofoam had better resilience than EPS geofoam. Under the laboratory multi-impact tests, the buffer performance of the sand-EPE composite cushion performed well under the multi-impacts. However, for the sand-EPS composite cushion, the buffer performance became poor with increased impact number. For the thicker geofoam, the buffer performance of the composite cushion changed slightly from the second impact to the fifth impact, especially for the EPE geofoam. Finally, large-scale rockfall experiments were carried out to further study the buffer performance of different cushions. Compared with EPS geofoam, EPE geofoam was more suitable for improving the capability of the composite cushion to resist multi-impacts, as well as to protect the rock-shed under multiple rockfall impacts.