ABSTRACT:

Despite over four decades of research into rock mass and discontinuity characterization, there are still no standardized methods for field characterization of discontinuity persistence and in particular intact rock bridges. As part of an ongoing project at Simon Fraser University, three open pit mines and one natural slope were investigated using digital photogrammetry, ground- based LiDAR, and modified discontinuity survey methods. The investigation had the specific objective of assessing discontinuity persistence and potential for intact rock bridges. Discontinuity surveys were carried out on 3-dimensional terrain models and on 2- dimensional trace maps at bench, inter-ramp, and overall pit slope scales. Modification to the field methodology were trialed based on contrasts in lithology, bench condition, and structural environments at the four sites. The results are being used to develop preliminary recommendations for an adaptable methodology for assessing discontinuity persistence and intact rock bridge content, which may be customized according to site pecific requirements, geological conditions, and the tools available to the practitioner.

1. INTRODUCTION

The development of open pit mines approaching depths of 1 km or more has brought renewed attention to the uncertainty inherent in estimating the persistence of adverse structures and the influence of intact rock bridges on their shear strength. As part of an ongoing project at Simon Fraser University, three open pit mines, and one natural rock slope were investigated using modified discontinuity survey methods remote sensing. The principal objective of this work was to assess varied approaches for discontinuity persistence and intact rock bridge Supplementing traditional field mapping techniques with modern remote sensing methods, a more inventory of rock mass discontinuities can be acquired The resultant remote sensing derived terrain models also provide helpful means for assessing block characteristics and variation in discontinuity-rock bridge configurations across bench, inter-ramp and overall pit slope scales.

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