Giovanni Leucci Nondestructive Testing for Archaeology and Cultural Heritage A Practical Guide and New Perspectives Nondestructive Testing for Archaeology and Cultural Heritage Giovanni Leucci Nondestructive Testing for Archaeology and Cultural Heritage A Practical Guide and New Perspectives 123 GiovanniLeucci Institute for Archaeological andMonumentalHeritage National Research Council Lecce,Italy ISBN978-3-030-01898-6 ISBN978-3-030-01899-3 (eBook) https://doi.org/10.1007/978-3-030-01899-3 LibraryofCongressControlNumber:2018958488 ©SpringerNatureSwitzerlandAG2019 Thisworkissubjecttocopyright.AllrightsarereservedbythePublisher,whetherthewholeorpart of the material is concerned, specifically the rights of translation, reprinting, reuse of illustrations, recitation, broadcasting, reproduction on microfilms or in any other physical way, and transmission orinformationstorageandretrieval,electronicadaptation,computersoftware,orbysimilarordissimilar methodologynowknownorhereafterdeveloped. The use of general descriptive names, registered names, trademarks, service marks, etc. in this publicationdoesnotimply,evenintheabsenceofaspecificstatement,thatsuchnamesareexemptfrom therelevantprotectivelawsandregulationsandthereforefreeforgeneraluse. The publisher, the authors and the editors are safe to assume that the advice and information in this book are believed to be true and accurate at the date of publication. Neither the publisher nor the authorsortheeditorsgiveawarranty,expressorimplied,withrespecttothematerialcontainedhereinor for any errors or omissions that may have been made. The publisher remains neutral with regard to jurisdictionalclaimsinpublishedmapsandinstitutionalaffiliations. Cover illustration: The roman amphitheatre of Catania: Reconstructive hypothesis with the various entrances to the monument. The research undertaken by IBAM-CNR between 2014 and 2015 aimed towardsobtainingathree-dimensionalreconstructionofthemonumentbycombiningdiversemethods (virtual archaeology, digital archaeology, NDT integrated technologies) of data acquisition and processing. This made it possible to acquire important data for the creation of an exact reproduction of the parts of the monument that are still hidden and provide a faithful reconstruction of the entire architectural structure. The virtual reconstruction was performed by the Information Technologies Laboratory (ITLab) of the IBAM-CNR (itlab.ibam.cnr.it) (with kind permission of Arch Francesco GabellonescientificdirectorofITLab_IBAM-CNR). ThisSpringerimprintispublishedbytheregisteredcompanySpringerNatureSwitzerlandAG Theregisteredcompanyaddressis:Gewerbestrasse11,6330Cham,Switzerland Preface Inthefieldofarchaeologicalresearchandtherestorationofmonumentalheritages, the importance of nondestructive testing (NDT) survey techniques has already become widely acknowledged. Theabilitytogaugetheextentofarchaeologicaldeposits,ortoassessartefacts’ stateofpreservationwithoutresortingtodisruptiveactivities,isextremelyusefulin terms ofbetterunderstandinga given siteandapproachingit inatargeted manner, for example, concerning both excavation and restoration operations. Accordingly, the purpose of this volume is to provide a general introduction to the most important NDT techniques for geophysical and micro-geophysical exploration methods, and to highlight their applications to archaeology and monumental her- itage. The book covers the physical principles, methodologies, interpretational procedures, and fields of application of the various survey methods. Moreover, it introducesnewinstrumentationandalgorithmsfordataacquisitionandprocessing, makingitausefulguideespeciallyfornewcomerstothefield,sinceextensivemath skills aren’t required for a general understanding of NDT methods. Whilewritingthebookforsuchabroadpotentialaudience,problemsinevitably arose concerning the appropriate level of mathematical treatment. The physical basisofthemethodsdiscussedisahighlymathematicalsubject;assuch,itrequired moreattentioninordertoshowthatnogreatmathematicalexpertiseisnecessaryfor a broad understanding of NDT surveying. That being said, in order to grasp the more advanced data processing and interpretation methodologies in depth, some level of mathematical ability is nonetheless required. The approach usedin this bookemploysthe simplestpossible mathematics and reduces mathematical analysis to very straightforward cases. However, users employing this approach to NDT methods should also be familiar with the more advanced techniques for analysing and interpreting NDT data, as they can greatly increase the amount of useful information obtained from the data. Therefore the approachusedinthebookwillenablethereadertoassessthescopeandimportance of the advanced techniques of analysis without entering into the details of their implementation. v vi Preface Examples are taken from measurement campaigns at sites of significant histor- ical archaeological importance, both at the national and international level. By exploring these examples, the reader will come to understand how to design and perform an NDT survey. Guidance is provided on choosing the most suitable methodforagiventypeofproblem,andonfindingthetypeofdataacquisitionand processing that will deliver the best possible results. In turn, the book describes the most innovative data acquisition and processing systems, which allow rapid reconnaissance of subterranean layers, and produce highly detailed evidence, even in very challenging cases. Itishopedthatthebookwillofferavaluableguideforstudentsofarchaeology, geophysics, architecture, and the engineering disciplines, as well as for specialists seeking to increase their expertise in this fantastic discipline. Lecce, Italy Giovanni Leucci Acknowledgements The author wishes to thank Dr. Lara De Giorgi for her invaluable collaboration during data acquisition, as well as the experts on the Pompeii Sustainable PreservationProject’sinternationalcommittee.Lastly,theauthorwishestoexpress his heartfelt thanks to Professor Jeroen Poblom, Director of the Belgian archaeo- logical mission in Sagalassos, for the opportunity to perform geophysical mea- surements, and for his valued support during the surveys. vii Contents 1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 2 Principles of Mathematics Used in NDT Methods. . . . . . . . . . . . . . . 7 2.1 Initial Considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 2.2 NDT Geophysical Data Digitalization . . . . . . . . . . . . . . . . . . . . . 8 2.3 Spectral Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 2.4 A Few Definitions to Remember . . . . . . . . . . . . . . . . . . . . . . . . . 14 Reference. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 3 Nondestructive Testing Technologies for Cultural Heritage: Overview. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 3.1 NDT Methods in Cultural Built Heritage and Archaeology: State of the Art . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 3.2 NDT Geophysical Methods. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 3.2.1 The Ground-Penetrating Radar Method. . . . . . . . . . . . . . . 21 3.2.2 The Electrical-Resistivity Active Method . . . . . . . . . . . . . 44 3.2.3 The Induced-Polarization Method . . . . . . . . . . . . . . . . . . . 54 3.2.4 The Self-potential Method . . . . . . . . . . . . . . . . . . . . . . . . 58 3.2.5 Seismic Method. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69 4 NDT Geophysical Instrumentation and Data Acquisition and Processing Enhancement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75 4.1 GPR Instrumentation Enhancement: Reconfigurable Stepped-Frequency Georadar. . . . . . . . . . . . . . . . . . . . . . . . . . . . 75 4.2 The GPR Data Acquisition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78 4.2.1 The GPR Frequency of Antenna and Depth of Penetration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79 4.2.2 The GPR Frequency of Antenna and Resolution . . . . . . . . 84 4.2.3 The Sampling Interval of Data Acquisition . . . . . . . . . . . . 85 4.2.4 The Two-Way Time Window Set. . . . . . . . . . . . . . . . . . . 85 ix x Contents 4.2.5 Sampling Interval . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86 4.2.6 Sample Spatial Interval . . . . . . . . . . . . . . . . . . . . . . . . . . 86 4.2.7 Survey Profiles Spacing and Orientation . . . . . . . . . . . . . . 87 4.3 GPR Data Processing Methodology. . . . . . . . . . . . . . . . . . . . . . . 88 4.4 GPR Data Visualization: Time Slices. . . . . . . . . . . . . . . . . . . . . . 94 4.5 GPR Data Visualization: Amplitude ISO-Surfaces . . . . . . . . . . . . 94 4.6 Electrical-Resistivity Tomography Field Measurements. . . . . . . . . 96 4.6.1 ERT Survey-Instrument Parameters. . . . . . . . . . . . . . . . . . 96 4.6.2 Choice of the Best Array . . . . . . . . . . . . . . . . . . . . . . . . . 100 4.6.3 ERT Survey Procedures. . . . . . . . . . . . . . . . . . . . . . . . . . 104 4.6.4 ERT Data Inversion. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111 4.7 Induced-Polarization Data Acquisition and Inversion . . . . . . . . . . 113 4.8 Self-potential Data Acquisition and Inversion. . . . . . . . . . . . . . . . 116 4.9 Seismic Sonic and Ultrasonic Data Acquisition and Inversion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 120 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 128 5 NDT Geophysical Data Interpretation . . . . . . . . . . . . . . . . . . . . . . . 131 5.1 GPR Data Interpretation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 131 5.2 ERT Data Interpretation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 140 5.3 IP Data Interpretation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 146 5.4 SP Data Interpretation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 149 5.5 Interpretation of Seismic and Ultrasonic Data. . . . . . . . . . . . . . . . 158 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 165 6 Site Application: The Archaeological Site of Pompeii (Italy). . . . . . . 169 6.1 Site History . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 169 6.2 Site Natural Hazard . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 172 6.3 NDT Geophysical Surveys . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 173 6.3.1 Area 1: GPR, ERT and SP Data Interpretation . . . . . . . . . 175 6.3.2 Area 2: GPR, ERT and SP Data Interpretation . . . . . . . . . 177 6.3.3 Area 3: GPR, ERT, and SP Data Interpretation . . . . . . . . . 179 6.3.4 The NDT Geophysical Survey of Tomb D . . . . . . . . . . . . 181 6.3.5 2D ERT Data Analysis and Interpretation . . . . . . . . . . . . . 182 6.3.6 ERT Data Analysis and Interpretation of the Wall of the Studied Tomb . . . . . . . . . . . . . . . . . . . . . . . . . . . . 185 6.3.7 Seismic Tomography Data Analysis and Interpretation of the Wall of the Studied Tomb . . . . . . . . . . . . . . . . . . . 187 6.3.8 2D GPR Data Analysis and Interpretation. . . . . . . . . . . . . 189 6.3.9 3D GPR Data Analysis and Interpretation. . . . . . . . . . . . . 190 6.4 GPR Data Acquisition and Analysis on the Columns . . . . . . . . . . 191 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 194 Contents xi 7 Site Application: The Archaeological Site of Sagalassos (Turkey) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 197 7.1 Site Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 197 7.2 NDT Geophysical Data Acquisition, Processing and Interpretation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 199 7.2.1 Area 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 200 7.3 The Roman Bath Stability Study . . . . . . . . . . . . . . . . . . . . . . . . . 204 7.3.1 Zone 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 205 7.3.2 Zone 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 209 7.3.3 Analysis of the Probability of Long-Term Collapse . . . . . . 210 7.4 Area 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 213 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 215 8 Conclusions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 217 Appendix: MATLAB Codes for NDT Geophysical Data Analysis.. .... 221 Index .... .... .... .... .... ..... .... .... .... .... .... ..... .... 239
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