Abstract
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.
Highlights
Rockfall sources during open pit operations can be ubiquitous and extremely difficult to predict [1]
Controlling rockfall hazards is a requirement for safe pit operations, as these pose risks to personnel and equipment [3,4], and are primarily controlled through bench geometry [1,5,6]
Depending on the geometry of the ore body, topography and lease boundaries; rockfalls and flyrock can be contained within the pit boundaries (Figure 1a) or the possibility remains for falling material to exit these boundaries (Figure 1b)
Summary
Rockfall sources during open pit operations can be ubiquitous and extremely difficult to predict [1]. Depending on the geometry of the ore body, topography and lease boundaries; rockfalls and flyrock can be contained within the pit boundaries (Figure 1a) or the possibility remains for falling material to exit these boundaries (Figure 1b) In the latter case, elements downslope from operations (e.g., mining components, sites of cultural importance, sensitive environmental areas, land owned by third parties) could be exposed to falling rock. TThhee ggeenneerraall wwoorrkk flflooww ffoorr tthhee mmeetthhoodd iiss pprreesseenntteedd iinn FFiigguurree22..ThTehemmetehtohdodstastratsrtlsevleevraergaingginignfionrfmoramtiaotniocnomcommomnotno mtoinmininginogpeorpaetiroantiso, nins,cliundclinugdihnigghh-irgehs-orleustoioluntidoingidtailgietlaelvealteiovnatmionodmelosd(eDlsEM(D)E(M1 t)o(15 tmo r5emsolruetsioolnu,titoynp,ictaylplyicasllyelaesvaetlieovnatriaosnterra)s, taeerr)i,aaleprihaol tpohgoratopghrya,pphiyt,lpayitoluaty(oauntd(apnhdaspehsa, sdees-, pdepndenindginognotnhethleevleevleolfotfetmempoproarladl edteatialiflofrorththeeaannaalylyssisis),),aannddssiitteeiinnvveessttiiggaattiioons (e.g., site reconnaissance for fallen rock blocks, unstablee ssllooppeess,, eettcc..)) This information is used to develop thematic maps, including the study area within the scope of work, slope iinncclination vvaalues, ttooppoographic rroouugghhnness ((nnaammeed ttooppooggraphic contrast) and soil and vegetation cover. Air photos can be used to identify active talus deposits and active rockfall paths (path identified due to scarce vegetation)
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