2015 TRANSACTIONS • Vol. 338 SOCIETY FOR MINING, METALLURGY & EXPLORATION 112 112 • 2015 TRANSACTIONS OF THE SOCIETY FOR MINING, METALLURGY & EXPLORATION Ground rippability classification by decision trees S.R. Dindarloo * Ph.D. candidate, Department of Mining and Nuclear Engineering, Missouri University of Science and Technology, Rolla, MO, USA * Corresponding author email: srd5zb@mst.edu E. Siami-Irdemoosa Ph.D. candidate, Department of Geosciences and Geological and Petroleum Engineering, Missouri University of Science and Technology, Rolla, MO, USA Abstract Ease of excavation or rippability, also called diggability or excavatibility, is a critical decision-making parameter in the selection of both the overburden removal method and the required equipment in surface mining and geotechnical engineering projects. The most widely used method of estimating rip- pability is rock mass classiication. Although there are different classiication schemes in the literature, all of them have the two major limitations of sharp transitions at class boundaries and subjective un- certainties in decision making. In this study, the decision trees method was employed as a classiication tool for estimating ground rippability, using the four rock mass parameters of weathering degree, uni- axial compressive strength, joint spacing and bedding spacing. The results were compared with those of the widely used method of diggability index rating (DIR) and a fuzzy-based DIR. The problem of subjective uncertainty was resolved in the proposed decision trees method, as the tree rules were derived automatically from the training data sets. Compared with fuzzy-DIR, a decision tree classiier is sim- pler, needs less computational time and is more appreciable by industry practitioners. Nevertheless, the proposed method is not lawless and, similar to both the conventional and fuzzy DIR methods, yielded poor estimations in particular instances. The limitations of the three methods are discussed. Introduction Determining the ease of ground excavation, called rippa- bility, diggability or excavatibility, is a critical decision-mak- ing step in selecting both the overburden removal method and equipment in surface mining and geotechnical engi- neering projects. Surface preparation is a primary phase in many geotechnical-geomechanical engineering projects and is performed in two major ways: (1) by drilling and blasting, and (2) by digging and ripping. In urban and environmen- tally sensitive sites, use of the drilling and blasting method is highly restricted, leaving the mechanical digging and ripping method as the only option. The proper selection and sizing of the machinery, such as dozer–rippers, is essential to project success. Economic, environmental and ground conditions are the most important constraints in equipment selection and sizing. From the technical point of view, the ground or rock mass properties are the dominant parameters in equipment selection. Many researchers have addressed the issue, using different methods. Basarir and Karpuz (2004) classiied the ground rippability estimation methods into two groups of di- rect and indirect methods. When proper equipment for trial tests is available, ripping tests can be implemented directly. Alternatively, if direct ripping runs cannot be conducted, the indirect methods are used to estimate ground rippability from the rock mass geomechanical properties. The major methods of indirect rippability estimations are seismic, graphical and ranking/classiication. Seismic methods. Estimation of rippability from seismic wave velocity is among the earliest attempts in this ield. The underlying theory of the method is that p-waves travel faster in denser rocks than in loose materials. A measurement of p- wave velocity in an area can classify the rock mass to differ- ent levels of rippability. Bailey (1975) used the seismic wave velocity in a rock mass to predict ground rippability. McCann and Fenning (1995) examined the effectiveness of using seis- Paper number TP-15-015. Original manuscript submitted April 2015. Revised manuscript accepted for publication October 2015. Discussion of this peer-reviewed and approved paper is invited and must be submitted to SME Publications Dept. prior to Sep. 30, 2016. Copyright 2016, Society for Mining, Metallurgy and Exploration Inc. Key words: Ground rippability, Diggability Index Rating, Fuzzy set theory, Decision trees, Rock mass classification 2015 Transactions of the Society for Mining, Metallurgy & Exploration, Vol. 338 (in press).