Consideration of secondary blocks in key-block analysis

Abstract

The mechanical and geometrical properties of rock and fractures control many aspects of mining. Rock, unlike artificial materials, is heterogeneous and anisotropic, which leads to complex mechanical responses. The unavoidable simplifications that we are forced to make when describing rock, and in particular, the fractures in rock, is one of mining's and blasting's enduring problems. However, it is now possible to model rock discontinuities much more accurately and realistically through discrete fracture models. Discrete fracture models consist of deterministic and stochastic components. The deterministic component comprises those faults and joints that have been explicitly mapped or detected from boreholes, geophysics or underground mapping. However, the model may also include a portion of the rock mass that has not been directly sampled. This portion of the rock is represented by “stochastic fractures”, which are fractures that have the same statistical distributions and geological correlations as the deterministic fractures. The new generation of sophisticated three-dimensional discrete fracture models can reproduce the true geological complexities of fractures, including their spatial distribution, size, orientation, roughness, aperture, and fluid flow or mechanical properties. This information alone has valuable application in support and damage calculations, and provides valuable input to a variety of analyses. This paper describes two potential applications of realistic fracture modeling: roof and wall support and blast damage control.