Assessment and prevention on the potential rockfall hazard of high-steep rock slope: a case study of Zhongyuntai mountain in Lianyungang, China

Artificially excavated rock slope of Zhongyuntai Mountain in Lianyungang is close to the busy Dongshugang expressway, with steep topography and well-developed structural planes. Under the influence of rain erosion, weathering, and human activities, it has high rockfall potential and seriously endangers road traffic safety. The purpose of this study is to conduct a preliminary assessment of the potential rockfall hazards in the slope area to provide support for the improvement and perfection of relevant protective facilities. Through the geological survey, numerical simulation and analysis of the structural features of the discontinuities, the main failure mechanisms of the rockfall investigated in this rock slope can be divided into weathering damage, planar failure, wedge failure and toppling failure. Accordingly, three potential rockfall source areas and possible rockfall movement profiles were determined. Rockfall hazard analysis and protective measures test were conducted using Rocfall v.4.0 software. Before that, the mass of the blocks for simulation analysis is selected as 4000 kg through survey statistics, and the normal and tangential restitution coefficients of five slope materials involved in each profile required by the numerical model are determined by on-site rockfall tests. Numerical simulations adopting these parameters were performed, and the bounce heights, roll-out distances, kinetic energies and the velocities of rockfall along the slope profiles were obtained. Based on the analysis of the simulation results, under the condition of no protective measures, 57.7–61.6% of the rocks intruded into the road along with the three profiles, and the maximum bouncing heights of the rockfalls on the three profiles could reach 23.52–26.52 m. The velocity and total kinetic energy of rockfall showed a clear increasing trend with the increase in the falling height. The maximum kinetic energies of rockfalls on the three profiles can reach 1680.7–2435.3 kJ, and even in the highway area, which can reach 1252.4–1711.3 kJ. Only a few rockfalls escaped under the existing protective measures, but for larger-sized rockfalls, the existing measures may face great challenges. These results obtained in this research may provide a useful reference for the reinforcement of slope prevention measures and the mitigation of rockfall hazards in similar potential areas.