Forecasting vulnerability of deep extraction level excavations to draw-induced cave loads

Abstract

Abstract Block and panel caving methods are increasingly used for mining of large and strong orebodies at large depths below the ground surface (>1\xa0km). This paper focuses on the production phase of caving when the extraction level is fully developed and subjected to the weight of overlying caved material. A limit equilibrium solution for estimation of cave loads is critically reviewed and combined with existing empirical tools in order to forecast extraction level performance under cave loading. The analysis results, presented in nomogram form, suggest that the risk of severe squeezing of extraction level tunnels does not increase with cave depths below 500–1000\xa0m due to the beneficial effects of arching. Under normal extraction ratios (ER\xa0=\xa0∼50%), severe squeezing experienced from cave loads in deep mines appears to be unlikely in all but the weakest rock masses (σcm