1. INTRODUCTION Geomechanical properties of discontinuities generally control the engineering behavior of rock masses. Discontinuities, defined as any mechanical break that has zero or relatively low tensile strength in a rock mass, are the most common weakness features in a rock mass. Discontinuity features include joints, fractures, fissures, foliations, weak bedding planes, and faults [1]. In geotechnical engineering projects, discontinuities are responsible for the most common challenges in the design of engineered structures in rocks. Therefore, engineered structures constructed in or on rock require proper site characterization of discontinuous rock masses [2]. Field characterization of discontinuity properties include collection of data for different parameters such as orientation, spacing, persistence, roughness, wall strength, aperture, infilling material, seepage, and number of joint sets. Typically, a large database is necessary to accurately represent site discontinuities. Data collected from these studies can later be used in numerical modeling, excavation and support design, and other engineering design works. In open pit mines, bench slope stability studies consist of collecting data pertinent to intact and discontinuous rock masses. One of the most critical properties of discontinuities is their orientation in space relative to both each other and the bench slope face [3]. Similarly oriented planes of weakness generally cluster around one or more ‘discontinuity sets’ or ‘families’ [4]. The identification of these sets is an important step in the discontinuity characterization process. In pit bench slopes, unfavorably oriented discontinuities can result in small to large scale failures that create dangerous working conditions. Therefore, an accurate representation of discontinuity set orientations can aid in slope stability prediction and analysis. Orientation data plotted on stereonets can be used to determine potential failure mechanisms. Figure 1 shows the kinematic analysis technique given by Hoek and Bray [5]. While collecting discontinuity data, it is necessary to obtain a large data set that accurately represents the sites ARMA 13-663 Discontinuity mapping using Ground-Based LiDAR: Case study from an open pit mine Tiruneh, H.W. and Stetler, L.D. Department of Geology and Geological Engineering, South Dakota School of Mines and Technology, Rapid City, SD, USA Oberling, Z.A., Morrison, D.R., Connolly, J.L., and Ryan, T.M. Call and Nicholas, Inc., Tucson, AZ, USA Copyright 2013 ARMA, American Rock Mechanics Association This paper was prepared for presentation at the 47 th US Rock Mechanics / Geomechanics Symposium held in San Francisco, CA, USA, 23-26 June 2013. This paper was selected for presentation at the symposium by an ARMA Technical Program Committee based on a technical and critical review of the paper by a minimum of two technical reviewers. The material, as presented, does not necessarily reflect any position of ARMA, its officers, or members. Electronic reproduction, distribution, or storage of any part of this paper for commercial purposes without the written consent of ARMA is prohibited. Permission to reproduce in print is restricted to an abstract of not more than 200 words; illustrations may not be copied. The abstract must contain conspicuous acknowledgement of where and by whom the paper was presented. ABSTRACT: Discontinuity data of rock masses are critical for the characterization, design, and analysis of rock fabrics as related to small- and large-scale slope stability. They present the most common challenges in the design of open pit mines as adverse rock fabric orientations may impart instabilities that have the potential to cause losses of life, infrastructure, and decrease in productivity. Therefore, accurate and precise characterizations of discontinuities are a crucial step in successfully designing stable slopes. Terrestrial LiDAR scanning coupled with high resolution images can be used for virtual mapping of discontunities. The benefits of implementing LiDAR as concerned with discontinuity mapping include ease of operation, improved safety, ability to collect data in inaccessible areas, short data acquisition time relative to manual data collection, and most importantly, pertinent rock mass data may be collected in much greater detail. A case study from an open pit mine was performed to evaluate if correlations exist among discontunity properties collected using different methods including (1) traditional cell mapping, (2) optical and acoustic borehole imaging (OBI and ABI, respectively) with sampled core and, (3) high resolution LiDAR scanning. The advantages and disadvantages of these techniques are discussed and recommendations based on the results are presented in this study.