Impact performance of unreinforced and geogrid-reinforced rockfall protection embankment

Abstract

This study designs and analyzes a Rockfall Protection Embankment (RPE) for an unstable slope in the Indian state of Mizoram. Initially, an in-depth trajectory analysis of the site is conducted to determine impact velocity, bounce height, and kinetic energy of falling rocks. Subsequently, the dimensions of three RPE variants-unreinforced, primary geogrid-reinforced, and secondary geogrid-reinforced configurations are determined based on literature and guidelines. Dynamic analyses are performed on these RPE variants using three-dimensional Finite Element software, PLAXIS 3D. The assessments consider multiple direct impacts and rebound impacts involving the maximum evaluated kinetic energy. Performance is assessed by examining maximum and residual deformations, mobilized tensile forces within geogrid layers, and the number of impacts the RPEs can withstand before reaching a deformation threshold. The results show that the reinforced RPE configurations exhibit significantly enhanced performance, withstanding nearly 20–43 times more impacts than unreinforced ones under both direct and rebound impact conditions. The inclusion of reinforcement layers notably improves the RPEs' ability to mitigate deformations by providing a confining effect to the soil mass and dissipating a part of the impact energy through the geosynthetics' strain and frictional resistance, thus making them more effective for rockfall protection.