Sublevel caving (SLC) is most effective under specific geological conditions characterized by:
Orebody geometry and dip: SLC is particularly suited for steeply dipping ore bodies, generally greater than 60°, and can also be applied to very thick and massive deposits. The orebody is typically divided into vertical slices for systematic extraction from top to bottom.
Rock mass cavability: Successful SLC depends heavily on the ability of the hangingwall rock mass to cave spontaneously or be blasted after ore extraction. The rock above the ore must cave consistently to fill the void left by mined ore. Cavability is influenced by rock mass conditions and the hydraulic radius of the mining footprint. Both stress caving and subsidence caving mechanisms are involved, with the caving rate needing to exceed the rate of rock damage to maintain stability.
Rock strength: Strong ore bodies are preferred because they can support narrower pillars, reducing dilution and improving ore recovery. Stronger rock also requires less support and allows better draw control.
Hangingwall conditions: the hangingwall must cave continuously to prevent voids and sudden collapses. Weak to strong hangingwalls are acceptable as long as they cave properly. This caving leads to surface subsidence, which must be managed carefully to avoid damage to surface infrastructure.
Geotechnical stability and subsidence management: the method is sensitive to geotechnical properties such as rock hardness, structural integrity, and groundwater conditions. Continuous caving is crucial to prevent large voids and sudden collapses underground and on the surface, which can cause significant subsidence and surface deformation.
Operational and design factors: while geological conditions are primary, operational discipline, draw control, and mine design parameters (e.g., drive width, level spacing) also influence the success of SLC. However, orebody geometry, host rock strength, overburden cover, and geotechnical conditions are the most significant factors affecting recovery and dilution.
In summary, sublevel caving is most effective in steeply dipping, strong ore bodies with rock masses that have good cavability, allowing controlled and continuous caving of the hangingwall. Proper management of subsidence and geotechnical stability is essential for safe and efficient operation.
