The key-group method

This paper proposes an extension to the key-block method, called 'key-group method', that considers not only individual key blocks but also groups of collapsable blocks into an iterative and progressive analysis of the stability of discontinuous rock slopes. The basics of the key-block method are recalled herein and then used to prove how key groups can be identified. We reveal that a key group must contain at least one basic key block, yet this condition is not entirely sufficient. The second block candidate for grouping must be another key block or a block whose movement-preventing faces are common to one or more single key blocks. We also show that the proposed method yields more realistic results than the basic key-block method and a comparison with results obtained using a distinct element analysis demonstrates the ability of this new method. Copyright (C) 2003 John Wiley Sons, Ltd.