MOBILE ANCHORS FOR CABLE YARDING SYSTEMS BEN LESHCHINSKY MARK L. RUSSELL Developed in Partnership between Oregon State University and the USDA Forest Service National Technology & Development Program OCTOBER 2016 THE AUTHORS Ben Leshchinsky, Ph.D., is an Assistant Professor in the Department of Forest Engineering, Resources and Management at Oregon State University, Corvallis, Oregon. Mark L. Russell, P.E., G.E., is a Civil/Geotechnical Engineer with the USDA Forest Service Technology and Development Program in San Dimas, California. ACKNOWLEDGEMENTS Funding for this report was provided by the U. S. Department of Agriculture, Forest Service and the Oregon Occupational Safety and Health Administration. The authors wish to thank the following individuals for their contribution to, and review of, this publication at various stages of development: • Michael B. Barger, Regional Logging Engineer, United States Forest Service, Region 6, Portland, Oregon • Edward Messerlie, Forest Management Program Leader, United States Forest Service, Technology and Development Program, Missoula, Montana • Clay Mancuso, M.F. Candidate, Department of Forest Engineering, Resources and Management, Oregon State University, Corvallis, Oregon • John Sessions, Professor of Civil Engineering, Oregon State University, Corvallis, Oregon • Jeffrey Wimer, Senior Instructor, Oregon State University, Corvallis, Oregon DISCLAIMER The mention of trade names or commercial products in this publication does not constitute endorsement or recommendation for use. TO ORDER COPIES An electronic version of this publication is available for download from ScholarsArchive@OSU: http://hdl.handle.net/1957/59796 Design and layout by Caryn M. Davis, Cascadia Editing, Philomath, OR Contact: [email protected] MOBILE ANCHORS FOR CABLE YARDING SYSTEMS BEN LESHCHINSKY MARK L. RUSSELL Developed in Partnership between Oregon State University and the USDA Forest Service National Technology & Development Program OCTOBER 2016 ABSTRACT Leshchinsky, B., and M.L. Russell. 2016. Mobile Anchors for Cable Yarding Systems. Oregon State University, Corvallis, OR. Cable yarding systems (also sometimes known as skyline yarding systems) are a versatile means for transporting materials in mountainous terrain in situations that do not allow for conventional harvesting methods such as ground skidding or shovel-logging. Adequate ground anchors are necessary for the safe operation of cable yarding systems. Anchored guylines stabilize the yarding tower enabling the safe transport of payloads. Typically, the anchors employed in these operations are available stumps or trees. Where adequate stumps or trees are not available, a vari- ety of alternative anchors can be applied. These includes buried deadman anchors, log decks, engineered earth anchors, rock bolts, and mobile equipment anchors such as bulldozers or skidders. This report provides an overview of cable yarding systems and the various anchor- ing systems that can be used to support them. The report describes mobile anchors in detail and presents the results of a series of physical load tests used to evaluate their stability. An analytical design solution for mobile anchor capacity based on force equilibrium analyses is presented. The information presented herein, including mobile anchor testing and analysis, is intended to serve as an instructive document outlining safe guidelines and consid- erations for implementation of mobile anchor systems. The intent is that this report and, most importantly, protect workers involved in cable yarding operations. and the field guide will expedite forest operations, reduce timber harvesting costs ii CONTENTS .................................................................................................................................................................................ii ...................................................................................................................................................................1 Abstract .......................................................................................................................1 1. Introduction .........................................................................................................................................1 1.1. Yarding Systems Overview ......................................................................................................................................................3 1.2. What is an anchor? ........................................................................................................4 1.3. Anchor Types ................................................................................................................................4 2. Overview of Anchor Types and Designs 2.1.1. Stump Anchor Guidelines ........................................................................................................................4 2.1. Stump or Tree Anchors 2.1.2. Load Capacity of Individual Stump Anchors..................................................................................5 ...........................................................................................................................7 2.2.1. Introduction ..................................................................................................................................................7 2.2. Buried Deadmen Anchors 2.2.2. Log Deadmen ................................................................................................................................................8 2.2.3. Precast Concrete Deadmen (Jersey Barriers) ............................................................................ 11 .................................................................................................................13 2.3.1. Introduction to Engineered Ground Anchors ............................................................................13 2.3. Engineered Ground Anchors 2.3.2. Friction and Helical Anchors ............................................................................................................13 2.3.3. Passive Earth Anchors .......................................................................................................................... 14 2.3.4. Picket Anchors .......................................................................................................................................... 14 2.3.5. Rock Anchors .............................................................................................................................................15 ................................................................................................................. 16 ...................................................................................................................... 16 2.4. Deck or Log-Bundle Anchors ......................................................................................................................................................... 18 2.5. Mobile Anchors Overview ........................................................................................................................18 3. Mobile Anchors 3.1.1. Mobile Anchor Theory ...........................................................................................................................18 3.1. Design of Mobile Anchors 3.1.1.1. Sliding ......................................................................................................................................................18 3.1.1.2. Overturning (Moment)....................................................................................................................20 3.1.1.3. Design Charts and Parameters ....................................................................................................23 .................................................................................................................................................23 ....................................................................................28 3.1.1.4. Example ..........................................................................................................................29 3.2. Summary of Mobile Anchor Field Testing .......................................................................................................................................32 3.3. Mobile Anchor Capacity 3.4.1. Mobile Anchor Movement as a Safety Advantage .....................................................................32 3.4. Anchor Movement 3.4.2. Mobile Anchor Movement ....................................................................................................................32 ................................................................................................................................................34 ...............................................................................................................35 3.5. Cable Loading .......................................................................................................................................................35 4. Conclusions and Recommendations .........................................................................................................................................35 4.1. Conclusions .........................................................................................................................................................................36 4.2. Recommendations