ABSTRACT:

This paper describes the extension of conventional wedge stability analysis techniques for slopes and underground excavations using Discrete Fracture Network (DFN) methods. DFN wedge analysis utilizes the same sets of kinematic equations as conventional wedge stability analyses, including the ability to model the impact of rock bolts, water pressure and earthquake movement. However, by more realistically modeling the geometry and properties of the structural features, the DFN wedge analysis has the potential to produce safer rock slope designs , and optimized support requirements for underground excavations. As in conventional wedge analysis, the DFN wedge approach uses Monte Carlo simulation to evaluate the wedges that could be formed on the basis of inferred fracture geometries. However, DFN wedge analysis is capable of modeling true three dimensional slope or underground geometries and more realistic fracture geometries. The result is an ability to optimize slope designs and support requirements with a method that intelligently handles the natural heterogeneity imposed by the fracture system.

INTRODUCTION

High resolution geophysics, borehole televiewers, optical borehole cameras, high resolution photography, laser scanning, and satellite imagery coupled with modern image processing techniques have dramatically improved our ability to accurately describe rock fabric. With relative ease, data can be acquired and processed that will provide a detailed description of key fracture properties such as fracture length, orientation, intensity, aperture and transmissivity. However despite the improvements in our ability to characterize the rock mass, the standard of practice for slope and tunnel kinematic analyses remains dependent on the generally unrealistic assumption of rock wedges being defined by ubiquitous, infinitely continuous fracture planes. Some available analytical tools allow the influence of intact rock bridges to be considered by distributing the rock bridge strength over the entire fracture area, however the size distribution and frequency of intact rock bridges must be assumed by the user. In reality, the presence of fractures in the rock mass is spatially variable, with their geometric, mechanical and hydraulic properties being more accurately described by statistical distributions. In response to the recent advances in the ability to characterize the spatial variability of rock mass structure, a Discrete Fracture Network (DFN) method of wedge analysis has been developed to provide a more robust, probabilistic approach to surface and underground wedge stability and ground support design

This content is only available via PDF.
You can access this article if you purchase or spend a download.