Empirical tools are based on local experience or on some geomechanical based classification systerm. Such systems should promote economical yet safe designs and must correctly be calibrated against case studies that are representative of the future applications. Methods have been available which relate the factors critical towards stope design to the estimated dilution. These are largely based upon relating critic parameters to observed stope behaviour. Non-entry mining methods such as open stoping are gaining increased prominence in Canadian mines.
Acceptable dilution is highly dependent upon grade.
A higher-grade stope can be economical however, a lower grade stope with the same dilution will no longer be feasible. Non-entry method of mining such as open stoping can accept a certain degree of wall slough without endangering mine personnel. While both methods rely heavily on a rock mass classification they differ in that the Stability Graph relies on data collected from several mine operations whereas the DilutionApproach relies upon information collected from one operation. This is an empirical method for open slope design proposed by Mathews et al. In its present form the Stability Graph links a stability number, N, to the hydraulic radius of the studied stope surface, Figure 2.