Generating and Measuring Prescribed Levels of Cohesion in Soil Simulants in Support of Extraterrestrial Terramechanics Research Laura Obregon University of Vermont
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University of Vermont ScholarWorks @ UVM Graduate College Dissertations and Theses Dissertations and Theses 2018 Generating And Measuring Prescribed Levels Of Cohesion In Soil Simulants In Support Of Extraterrestrial Terramechanics Research Laura Obregon University of Vermont Follow this and additional works at: https://scholarworks.uvm.edu/graddis Part of the Civil Engineering Commons Recommended Citation Obregon, Laura, "Generating And Measuring Prescribed Levels Of Cohesion In Soil Simulants In Support Of Extraterrestrial Terramechanics Research" (2018). Graduate College Dissertations and Theses. 832. https://scholarworks.uvm.edu/graddis/832 This Thesis is brought to you for free and open access by the Dissertations and Theses at ScholarWorks @ UVM. It has been accepted for inclusion in Graduate College Dissertations and Theses by an authorized administrator of ScholarWorks @ UVM. For more information, please contact [email protected]. GENERATING AND MEASURING PRESCRIBED LEVELS OF COHESION IN SOIL SIMULANTS IN SUPPORT OF EXTRATERRESTRIAL TERRAMECHANICS RESEARCH A Thesis Presented by Laura Obregon to The Faculty of the Graduate College of The University of Vermont In Partial Fulfillment of the Requirements for the Degree of Master of Science Specializing in Civil and Environmental Engineering January, 2018 Defense Date: November 8, 2017 Thesis Examination Committee: Mandar Dewoolkar, Ph.D., Advisor Darren Hitt, Ph.D., Chairperson Ehsan Ghazanfari, Ph.D. Cynthia J. Forehand, Ph.D., Dean of the Graduate College ABSTRACT Scientists have been well aware of the complexity of Martian and lunar regoliths. There are vast unexplored areas on both, the Moon and Mars, as well as uncertainties in our understanding of the physicochemical properties of their regoliths. Lunar and Martian regoliths differ from terrestrial soils in that they appear granular, but are expected to contain some cohesion. As such, cohesion in regolith poses challenges for future space operations, more specifically for landing, settlement, and mobility purposes. The ability to induce prescribed levels of cohesion in regolith simulants and reliably measure it would allow scientists to evaluate space technology limitations under different operational scenarios on Earth prior to a mission. Therefore, the objectives of this research were to (1) develop methods to induce prescribed levels of cohesion in dry granular media, and (2) evaluate accessible and reliable testing methods to measure cohesion. We developed and evaluated several methods to induce cohesion in two types of dry sand, F-75 silica sand and generic play sand. The methods to induce cohesion included play sand mixed with sugar-water, polymeric sand, and nanocellulose fibers, as well as F- 75 sand mixed with polydimethylsiloxane, polyvinyl acetate, crystalline silica, agar, zero- valent iron, adhesive spray, and sand surface modification using a plasma gun. Each method was assessed for advantages and disadvantages, and laboratory specimens produced using the most promising methods were tested at different compositions and densities to measure cohesion. The laboratory methods used to measure the cohesion included direct shear test, simple direct shear test, and vertical cut test. The results from these tests were then compared to tensile strength tests, using a split box test. In addition, these tests were also performed on lunar simulants JSC-1A and GRC-3 at different densities. The direct shear apparatus was available, but the other three devices were fabricated as part of this work. Based on the research results, simple methods to potentially induce low levels of cohesion in dry granular media are suggested along with suitability of laboratory methods to measure the added cohesion. ACKNOWLEDGEMENTS I would like to thank the Department of Civil and Environmental Engineering at UVM and the Vermont NASA Space Grant for their financial support. I am grateful to my advisor Dr. Mandar Dewoolkar for his guidance and tutelage throughout my time at UVM, as well as to my committee members, Dr. Ehsan Ghazanfari and Dr. Darren Hitt. I am thankful to Floyd Vilmont, Jake Kittell, and Bobby Farrell for building and putting together the testing devices for this research. I am also thankful to my collaborators at the Glenn Research Center, and for the advice from Dr. Rachel Oldisnki, Patrick Charron, Dr. Raju Badireddy, and Dr. Ting Tan. I am thankful to Pattie McNatt and Debra Fraser for their support. Special thanks to Drs. Stein Sture and Dobroslav Znidarcic for providing information on the University of Colorado split box device. Also, I would like to thank my officemates, Ian Anderson, and Matt Trueheart, and undergraduate researchers, Sydney Kahn, Dunia Karzai, Eliza Jobin-Davis, and Matt Stevens. Finally and most importantly, I would like to thank the support of friends and family especially my mom, my dad, my grandparents, Dr. John Hanley, Laurene and Buck Rogers, and Dr. Donna Rizzo. ii TABLE OF CONTENTS Page ACKNOWLEDGEMENTS .......................................................................................... ii CHAPTER 1: INTRODUCTION ................................................................................. 1 1.1 Problem Statement ........................................................................................ 1 1.2 Summary of Research Contributions ............................................................ 2 1.3 Thesis Outline ............................................................................................... 3 CHAPTER 2: Literature Review .................................................................................. 4 2.1 Regolith Cohesion and Space Exploration ................................................... 4 2.1.1 Vision for Future NASA Space Exploration ......................................... 4 2.1.2 Importance of Soil Cohesion for Space Exploration Technology and Missions .......................................................................................................... 5 2.1.3 Challenges from Planetary Cohesive Regolith ...................................... 7 2.1.4 Lunar Regolith Characteristics .............................................................. 8 2.1.5 Martian Regolith Characteristics ........................................................... 9 2.1.6 Theories behind Lunar and Martian Regolith Cohesion ...................... 10 2.2 Existing Methods to Measure Cohesion ..................................................... 13 2.3 Tensile Strength and Cohesion ................................................................... 15 2.4 Review of Laboratory Techniques for Soil Shear Strength Determination 17 2.4.1 Direct Shear Test.................................................................................. 17 2.4.2 Vertical Cut Test .................................................................................. 18 2.4.3 Simple Direct Shear Test ..................................................................... 20 2.5 Soil Tensile Strength Determination using Split Box Test ......................... 23 CHAPTER 3: Testing Methods Employed in this Research ...................................... 30 3.1 Introduction ................................................................................................. 30 3.2 Testing Devices ........................................................................................... 31 3.2.1 Direct Shear Test.................................................................................. 31 3.2.2 Simple Direct Shear Test ..................................................................... 33 3.2.3 Vertical Cut Test .................................................................................. 38 3.2.4 Split Box Test ...................................................................................... 42 3.3 Future Research for Testing Devices .......................................................... 45 iii CHAPTER 4: Simulants and Base Materials .............................................................. 48 4.1 Introduction ................................................................................................. 48 4.2 JSC-1A ........................................................................................................ 48 4.3 GRC-3 ......................................................................................................... 51 4.4 F-75 Fine Silica Sand .................................................................................. 53 4.5 Generic Play sand ....................................................................................... 53 4.6 Glass Beads ................................................................................................. 55 CHAPTER 5: Laboratory Methods Explored to Induce Cohesion in Dry Granular Media ............................................................................................. 56 5.1 Introduction ................................................................................................. 56 5.2 Methods Explored ....................................................................................... 56 5.2.1 Sand Mixed with Sugar-water ............................................................. 56 5.2.2 Sand Mixed with Nanocellulose Fibers ............................................... 57 5.2.3 Sand Mixed with Polymeric Sand........................................................ 58 5.2.4 Sand Mixed with Agar Gel .................................................................