ABSTRACT: Many factors simultaneously influence stability and dilution in open stopes. This makes it difficult to assess the effect of individual changes to the rock mass condition or mining activity. Hangingwall stability is being studied at the Rabbit Lake Mine in Northern Saskatchewan. The influence of the rock mass condition, overall stope geometry and mining factors such as cable support are considered in this paper. Detailed analysis of 3-D stope survey data is used to accurately reflect the degree of instability for a given opening geometry, stress and rock mass condition. This stope survey data is coupled with detailed geology data to assess the influence of changing rock mass conditions away from the opening surface. This paper outlines an approach for gaining a better understanding of the factors influencing dilution based on detailed assessments of individual stopes, rather than a statistical assessment of many factors from a large data base of case histories.
1 INTRODUCTION
A key aspect of longhole open stope design is the prediction of the amount of overbreak or dilution that can be expected. Dilution is influenced by many factors controlled by both the mining and ground conditions. Mining controlled factors include, among other things, ground support, stope geometry, blasting method, stope sequencing, undercutting and time. In order to predict the dilution, some assumptions and generalities are required to estimate the rock properties. Underground openings in hard rock open stope mining are often designed using a well established procedure. Piteau (1973) states that the process begins with separating the rock mass into structural domains that are predicted to behave in a similar fashion or have similar properties. In general, these structural domains are relatively large, and they are based on lithological contacts or major zones of jointing or shearing.
