Site characterization and foundation design for the emplacement of radio telescope antennas at the Matjiesfontein Space Geodesy Observatory by Cornel Janse van Rensburg Thesis presented in fulfilment of the requirements for the degree of Master of Engineering in the Faculty of Engineering at Stellenbosch University Supervisor: Mr Leon Croukamp March 2017 Stellenbosch University https://scholar.sun.ac.za Declaration By submitting this thesis electronically, I declare that the entirety of the work contained therein is my own, original work, that I am the authorship owner thereof (unless to the extent explicitly otherwise stated) and that I have not previously in its entirety or in part submitted it for obtaining any qualification. Cornel Janse van Rensburg March 2017 Copyright © 2017 Stellenbosch University All rights reserved Department of Civil Engineering ii Stellenbosch University https://scholar.sun.ac.za Abstract The suitability of the Matjiesfontein Space Geodesy Observatory (MSGO) site for hosting radio telescope antennas is partially dictated by certain civil engineering considerations. These include the investigated geotechnical and hydrological site characteristics. The engineering properties of different soil and rock types in the surrounding area were also investigated as their use as construction material may have cost implications for the project. A GPS survey was carried out on the area earmarked for radio telescopes, which gave the researcher an opportunity to familiarize himself with the terrain and use the data for creating a digital terrain model (DTM) of the area. The geotechnical investigation followed and has shown encouraging results indicating shallow bedrock generally of hard to very hard rock consistency. This is a favourable founding condition for structures, but is particularly important in geodesy where instruments rely on stability to produce accurate results. The hydrological investigation has shown that, with even a very conservative steady flow analysis, the discharge in channels will not put infrastructure at risk of flooding in the event of heavy rainfall. Standard tests performed on local soil indicated a variety of soil types, mostly due to the different geomorphic processes in their origin as well as the varying geology in the area. Six disturbed samples of colluvial, alluvial and residual material were tested using the TMH1 (Technical Methods for Highways) to produce indicative characteristics of untreated local soil. They were then classified using the Unified Soil Classification System and the three main samples were classified for quality using TRH14 (Technical Recommendations for Highways). The materials were also evaluated as fine aggregate for concrete, selected fill for services and patching material for improving eroded sections of the access road. Petrographic results from a previous study indicated the presence of strained quartz in quartzitic sandstone from the site, rendering aggregate potentially susceptible to alkali-silica reaction. Tillite (Diamictite) of the Dwyka Formation in KwaZulu-Natal has also been identified as potentially reactive by laboratory testing. Quartzitic sandstone and tillite samples were subsequently collected from site and tested for alkali-silica reaction (ASR), resulting in almost none to innocuous expansion. These rocks were also tested for compressive strength, yielding strengths in excess of 70MPa. Based on these results and if found to be feasible, the possibility exists for loose boulders to be sourced, crushed and sorted locally for use as coarse aggregate in concrete, without causing any aesthetically displeasing affects to the environment. A limit state design (LSD) approach for a SKA-type radio telescope foundation was undertaken using nominal loads obtained from the organization and characteristic material properties obtained from this study. The foundation was designed as a circular spread gravity footing with a diameter of 5.5m, the size being governed by equilibrium at the ultimate limit state (ULS). The most important conclusion is that the site is, in terms of its engineering properties, certainly suitable for conducting radio astronomy and geodetic experiments. Stellenbosch University iii Stellenbosch University https://scholar.sun.ac.za Opsomming Die geskiktheid van die “Matjiesfontein Space Geodesy Observatory” (MSGO) terrein vir die huisvesting van radioteleskoop antennas word gedeeltelik bepaal deur sekere siviele ingenieursoorwegings. Dit sluit die ondersoekde geotegniese en hidrologiese eienskappe van die terrein in. Die ingenieurseienskappe van verskillende grond- en rotstipes in die omliggende gebied was ook ondersoek aangesien die gebruik daarvan as konstruksiemateriaal koste-implikasies vir die projek mag inhou. ’n “GPS” opname was uitgevoer in die area geoormerk vir radioteleskope, wat die navorser die geleentheid gebied het om homself te vergewis met die terrein en die data te gebruik om ’n digitale terrein model (DTM) van die terrein te skep. Die geotegniese ondersoek het daarna gevolg en het goeie resultate opgelewer wat dui op ’n goeie gehalte vlak rotsbedding van harde tot baie harde materiaal. Dit is 'n gunstige toestand vir strukture, maar is veral belangrik vir geodesie waar instrumente staatmaak op stabiliteit om akkurate resultate op te lewer. Die hidrologiese ondersoek het getoon dat, selfs met ’n baie konserwatiewe bestendige vloei analise, die afloop in kanale nie infrastruktuur in gevaar van oorstroming sal plaas in die geval van swaar reënval nie. Standaard toetse op plaaslike grond het gedui op ’n verskeidenheid van grondtipes, as gevolg van die verskillende geomorfologiese prosesse sowel as die wisselende geologie in die gebied. Ses versteurde monsters van kolluviale, alluviale en residuele grond is getoets met behulp van die TMH1 (“Technical Methods for Highways”) om voorlopige eienskappe van onbehandelde plaaslike grond te verkry. Daarna was dit geklassifiseer met behulp van die “Unified Soil Classification” sisteem en die drie belangrikste monsters is verder geklassifiseer met behulp van die TRH14 (“Technical Recommendations for Highways”). Die materiaal was geëvalueer as fyn aggregaat vir beton, opvulmateriaal vir dienste en pleister-materiaal vir die verbetering van geërodeerde dele van die toegangspad. Petrografiese resultate uit ’n vorige studie het die teenwoordigheid van gespanne kwarts aangedui in die sandsteen van die terrein, wat aggregaat moontlik vatbaar maak vir alkali-silika reaksie. Tilliet (Diamiktiet) van die Dwyka Formasie in KwaZulu-Natal is in die literatuur geïdentifiseer as potensieel reaktief. Kwartsitiese sandsteen en tilliet monsters is gevolglik versamel en getoets vir alkali-silika reaktiwiteit (ASR), met byna geen tot weglaatbare uitsetting. Dié rots was ook getoets vir druksterkte, met sterktes bo 70MPa. Op grond van hierdie resultate en indien dit uitvoerbaar is, kan los rotse plaaslik versamel, gebreek en sorteer word vir gebruik as growwe aggregaat in beton, sonder enige negatiewe ongewensde effekte op die omgewing. ’n Limietstaat ontwerp (LSD) benadering vir die fondasie van ’n SKA-tipe radioteleskoop was gedoen met behulp van nominale laste verkry vanaf die organisasie en karakteristieke materiaaleienskappe vanuit dié studie. Die fondasie is ontwerp as ’n ronde plat voetstuk met 'n diameter van 5.5m, bepaal deur ewewig by die uiteindelike limietstaat (ULS). Die hoof gevolgtrekking is dat die terrein geskik is, in terme van sy ingenieurseienskappe, vir die uitvoer van radio-astronomie en geodetiese eksperimente. Department of Civil Engineering iv Stellenbosch University https://scholar.sun.ac.za Acknowledgements I would like to express my deepest gratitude to Mr Leon Croukamp as my supervisor and for allowing me to take part in this project. I also want to thank Inkaba Ye’Afrika for the financial support they have offered me during this study. I further want to extend my gratitude to Dr Marius de Wet and Mrs Chantal Rudman for always being available to offer advice when needed. I want to thank Ms Susan Bothma for her aid in gathering and compiling the different survey datasets. I am very thankful towards Mrs Nanine Fouché for sharing her experience in core logging, which contributed greatly to this study. I want to thank Ms Danél van Tonder for her descriptions of the rock and mortar samples and for giving me the opportunity to look at the thin sections through the petrographic microscope. I want to thank Mr Salhin Alaud for introducing me to and letting me use his experimental setup for testing alkali-silica reactivity of aggregates and Mr Johan van der Merwe for his assistance in the design and production of the moulds. I would also like to thank Dr Bertie Oberholster and Mr Bertus Fonternel for their constructive discussions on the interpretation of the mortar-bar test and soil results, respectively. Furthermore, I want to express appreciation to Mr Pierre van der Spuy for sharing his knowledge on foundation design and Dr Peter Day for his review of the design along with the invaluable comments he made. The assistance provided by the geotechnical and transport laboratory staff is greatly appreciated. I also want to thank Roelof Lategan from Roadlab in Upington and Marjo Hofman from Geoscience Laboratories in Cape Town for their technical assistance and allowing me to use their facilities free of charge. I finally wish to thank the people from Matjiesfontein for their hospitality and everyone else who were kind enough to lend their support. Stellenbosch University v Stellenbosch University https://scholar.sun.ac.za Dedications It is with great gratitude that I dedicate this work and the degree that accompanies it to my loving parents, Louis and Luise Janse van Rensburg, whom have always supported me unconditionally. Department of Civil Engineering vi Stellenbosch University https://scholar.sun.ac.za Table of Contents Declaration ........................................................................................................................................... ii Abstract ...............................................................................................................................................iii Opsomming ......................................................................................................................................... iv Acknowledgements .............................................................................................................................. v Dedications .......................................................................................................................................... vi Table of Contents ............................................................................................................................... vii List of Figures ...................................................................................................................................... x List of Tables ...................................................................................................................................... xii List of Abbreviations ......................................................................................................................... xiv Chapter 1: Introduction ........................................................................................................................... 1 1.1 The town of Matjiesfontein .......................................................................................................... 1 1.2 The Matjiesfontein Space Geodesy Observatory .......................................................................... 3 1.3 Site description ............................................................................................................................. 3 1.4 Problem statement ........................................................................................................................ 4 1.5 Motivation for research ................................................................................................................. 4 1.6 Research aim ................................................................................................................................. 5 1.7 Research objectives ...................................................................................................................... 5 1.8 Limitations .................................................................................................................................... 5 1.9 Layout of report ............................................................................................................................ 6 Chapter 2: Literature Review .................................................................................................................. 7 2.1 Introduction .................................................................................................................................. 7 2.2 The radio telescope ....................................................................................................................... 8 2.2.1 Background.............................................................................................................................. 8 2.2.2 Radio telescopes in South Africa............................................................................................. 8 2.2.3 Very long baseline interferometry ......................................................................................... 10 2.3 Geology ...................................................................................................................................... 11 2.3.1 The rock cycle ....................................................................................................................... 11 2.3.2 The local geology .................................................................................................................. 12 2.3.3 Geohazards ............................................................................................................................ 16 2.3.4 The soil profile ...................................................................................................................... 17 2.4 Engineering properties of soil ..................................................................................................... 18 2.4.1 Particle distribution of soil .................................................................................................... 18 2.4.2 Plasticity of soil ..................................................................................................................... 19 2.4.3 Compaction............................................................................................................................ 20 2.5 Alkali-silica reaction ................................................................................................................... 22 Stellenbosch University vii Stellenbosch University https://scholar.sun.ac.za Table of Contents 2.6 Flooding ...................................................................................................................................... 23 2.7 Foundations ................................................................................................................................ 25 2.7.1 Type of foundations ............................................................................................................... 25 2.7.2 Design of foundations ............................................................................................................ 26 2.8 Summary ..................................................................................................................................... 28 Chapter 3: Methodology for Site Characterization ............................................................................... 29 3.1 Introduction ................................................................................................................................ 29 3.2 Field survey and sample collection ............................................................................................. 30 3.3 Geotechnical investigation .......................................................................................................... 32 3.3.1 Core logging .......................................................................................................................... 32 3.3.2 Rock mass rating ................................................................................................................... 32 3.3.3 Petrographic analysis ............................................................................................................. 33 3.4 Hydrological investigation .......................................................................................................... 34 3.4.1 Characteristics catchments .................................................................................................... 34 3.4.2 Flood calculation ................................................................................................................... 35 3.4.3 Flood plain analysis ............................................................................................................... 37 3.5 Tests on soil ................................................................................................................................ 37 3.5.1 Grading analysis .................................................................................................................... 38 3.5.2 Atterberg limits ...................................................................................................................... 41 3.5.3 Compaction test ..................................................................................................................... 43 3.5.4 California Bearing Ratio test ................................................................................................. 45 3.6 Tests on rock ............................................................................................................................... 47 3.6.1 Unconfined compressive strength and point load index tests ................................................ 47 3.6.2 Particle and relative densities ................................................................................................ 49 3.6.3 Mortar-bar test ....................................................................................................................... 50 Chapter 4: Results ................................................................................................................................. 54 4.1 Introduction ................................................................................................................................ 54 4.2 Digital terrain model and channel profiles ................................................................................. 55 4.3 Geotechnical results .................................................................................................................... 56 4.4 Hydrological results .................................................................................................................... 59 4.5 Results on soil ............................................................................................................................. 63 4.5.1 Grading analysis .................................................................................................................... 63 4.5.2 Atterberg limits ...................................................................................................................... 65 4.5.3 Compaction results ................................................................................................................ 67 4.5.4 California bearing ratio results .............................................................................................. 67 4.6 Results on rock ........................................................................................................................... 71 4.6.1 Unconfined compressive strength results .............................................................................. 71 Department of Civil Engineering viii Stellenbosch University https://scholar.sun.ac.za Table of Contents 4.6.2 Particle and relative density test results ................................................................................. 71 4.6.3 Mortar-bar test results ............................................................................................................ 71 4.7 Soil classification ........................................................................................................................ 72 4.7.1 Soil type ................................................................................................................................. 72 4.7.2 Material quality ..................................................................................................................... 74 4.8 Evaluation of soil and rock ......................................................................................................... 75 4.8.1 Concrete aggregate ................................................................................................................ 75 4.8.2 Fill material ........................................................................................................................... 77 4.8.3 Patching material ................................................................................................................... 78 Chapter 5: Foundation Design .............................................................................................................. 81 5.1 Introduction ................................................................................................................................ 81 5.2 Design methodology ................................................................................................................... 82 5.3 Nominal loads and characteristic material properties ................................................................. 83 5.3.1 Nominal loads ........................................................................................................................ 83 5.3.2 Characteristic material properties .......................................................................................... 84 5.4 Design criteria ............................................................................................................................. 85 5.4.1 Overall stability ..................................................................................................................... 85 5.4.2 Sliding resistance ................................................................................................................... 87 5.4.3 Bearing resistance .................................................................................................................. 88 5.4.4 Settlement .............................................................................................................................. 91 5.5 Final remarks .............................................................................................................................. 94 Chapter 6: Closure ................................................................................................................................ 95 6.1 Introduction ................................................................................................................................ 95 6.2 Conclusions ................................................................................................................................ 95 6.3 Recommendations....................................................................................................................... 97 Bibliography ..................................................................................................................................... 100 Appendix A: Subsurface Data............................................................................................................. 105 Appendix B: Hydraulic Data .............................................................................................................. 109 Appendix C: Petrographic Results ...................................................................................................... 114 Appendix D: Miscellaneous Results ................................................................................................... 124 Appendix E: Design Calculations ....................................................................................................... 137 Appendix F: Drawings ........................................................................................................................ 143 Appendix G: Photo Report .................................................................................................................. 146 Stellenbosch University ix Stellenbosch University https://scholar.sun.ac.za List of Figures Figure 1-1: Locality of Matjiesfontein .................................................................................................... 2 Figure 1-2: The Lord Milner in Matjiesfontein (L Croukamp) ............................................................... 2 Figure 1-3: The MSGO site (Google Earth) ........................................................................................... 3 Figure 1-4: Model of proposed positions for structures by Fourie et al. (2007) ..................................... 4 Figure 2-1: The electromagnetic spectrum ............................................................................................. 8 Figure 2-2: The radio telescopes at HartRAO (M Gaylard) ................................................................... 9 Figure 2-3: Map of global VLBI networks with HartRAO ..................................................................... 9 Figure 2-4: The concept of VLBI ......................................................................................................... 10 Figure 2-5: Annual movement of radio telescopes measured by geodetic VLBI (HartRAO, [s.a.]) .... 11 Figure 2-6: The rock cycle .................................................................................................................... 12 Figure 2-7: Field geology (scale 1:50 000) (Council for Geoscience) .................................................. 13 Figure 2-8: Tombstone weathered outcrops of Dwyka tillite ............................................................... 14 Figure 2-9: Particle size ranges in millimetre from Craig (2004) ......................................................... 18 Figure 2-10: The Atterberg limits ......................................................................................................... 19 Figure 2-11: Visual inspection on the access road by Kloos (2014) ..................................................... 21 Figure 2-12: Strained quartz in quartzitic sandstone by Van Wyk (2013) ............................................ 23 Figure 2-13: Shallow foundation types ................................................................................................. 25 Figure 3-1: Site characterization ........................................................................................................... 30 Figure 3-2: Key plan showing locations of retrieved soil and rock samples ........................................ 31 Figure 3-3: Drilling in progress ............................................................................................................ 32 Figure 3-4: The petrographic microscope ............................................................................................. 33 Figure 3-5: Main soil samples ............................................................................................................... 38 Figure 3-6: Rolling out of soil for determining plastic limit ................................................................. 42 Figure 3-7: Soil under compaction........................................................................................................ 43 Figure 3-8: Finishing sample after compaction .................................................................................... 44 Figure 3-9: Compression tests on sandstone and tillite ......................................................................... 48 Figure 3-10: Point load index correlation with UCS from Byrne & Berry (2008) ............................... 48 Figure 3-11: Pycnometer ....................................................................................................................... 49 Figure 3-12: Crushed sandstone and tillite ........................................................................................... 50 Figure 3-13: Graded aggregate ............................................................................................................. 52 Figure 4-1: Digital terrain model of the main study area ...................................................................... 55 Figure 4-2: Channel profiles ................................................................................................................. 55 Figure 4-3: Core logs from borehole 1 (top), borehole 2 (middle) and borehole 3 (bottom)................ 56 Figure 4-4: Borehole logs ..................................................................................................................... 57 Figure 4-5: Extract from topographical map showing catchments (NTS) ............................................ 59 Department of Civil Engineering x