Rock Fall Hazard Analysis for In-Pit Operations Potentially Impacting External Sensitive Areas

Controlling rockfall-related risks is a requirement for safe pit operations and primarily mitigated through adequate bench geometry design and implementation. This paper presents a method for rockfall hazard analysis for in-pit operations potentially impacting external sensible areas, adapted from natural rockfall hazard analyses. The method considers the natural susceptibility to rockfalls pre-mining, rockfalls originated from bench failures, and those initiated as flyrock. Rockfall trajectory models are used to estimate the potential for blocks reaching exposed elements. Natural susceptibility to rockfalls and trajectories are used as a baseline on which to evaluate the potential effects of open pit operations on the environment and perceptions of communities in the area. The method is illustrated for an open pit in steep terrain in the Peruvian Andes at a feasibility level of study. The paper illustrates the flexibility for including considerations of pre-mining rockfall impacts on the external elements of interest, and for developing rockfall mitigation strategies that consider rock block velocities, heights, energies and the spatial distribution of trajectories. The results highlight the importance of considering the three-dimensional effects of the terrain on block trajectories, and how such insights allow for increasing the efficiency of resources available for rockfall protection structures.

Full-scale testing and modeling of rock-shed shock absorbers under impact loads

Shock absorbers are often situated on top of rock-sheds to mitigate the effects of geological disasters such as rockfalls. In this study, three full-scale impact load tests, with impact energies of approximately 250, 500, and 1000 kJ, investigated a new type of shock absorber comprising expanded polystyrene, steel material, and sand cushion. Comparing the results of the full-scale tests with the results through sand cushion—a common material used for shock absorbers—the maximum impact load in this study was reduced by around 50% than the empirical formula suggested by a rockfall mitigation code. Besides, the study utilized LS-DYNA finite element software to find out the limitation of energy absorption, accuracy of simulation, input parameters for inferential impact formulas of the shock absorber, and to generate a reasonable simulation for use in further research and design of rock-sheds.

Comprehensive Mitigation and Control of Rockfall Hazard

Rockfall is one kind of important geohazard. Due to its complexity of trajectory, it is difficult for treatment designing in slope engineering. This paper employs a methodology for estimating rockfall trajectory using a series of established formulas, and then discusses the advantage and also disadvantage of existing controlling measures for rockfall mitigation. Based on site survey, calculation results and site geologic conditions, various protective structures such as retaining walls, safety net system and vegetation or plants, are suggested to mitigate and control the rockfall hazards comprehensively, which illustrates great advantages in technology, economics and environmental protection in a case study of rockfall hazard treatment. The idea and methodology presented herein is referential for similar slope problems.