{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,4,13]],"date-time":"2026-04-13T20:17:49Z","timestamp":1776111469585,"version":"3.50.1"},"reference-count":24,"publisher":"MDPI AG","issue":"10","license":[{"start":{"date-parts":[[2014,10,13]],"date-time":"2014-10-13T00:00:00Z","timestamp":1413158400000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Remote Sensing"],"abstract":"<jats:p>In railways Ground Penetrating Radar (GPR) studies, the evaluation of materials dielectric properties is critical as they are sensitive to water content, to petrographic type of aggregates and to fouling condition of the ballast. Under the load traffic, maintenance actions and climatic effects, ballast condition change due to aggregate breakdown and to subgrade soils pumping, mainly on existing lines with no sub ballast layer. The main purpose of this study was to validate, under controlled conditions, the dielectric values of materials used in Portuguese railways, in order to improve the GPR interpretation using commercial software and consequently the management maintenance planning. Different materials were tested and a broad range of in situ conditions were simulated in laboratory, in physical models. GPR tests were performed with five antennas with frequencies between 400 and 1800 MHz. The variation of the dielectric properties was measured, and the range of values that can be obtained for different material condition was defined. Additionally,  in situ GPR measurements and test pits were performed for validation of the dielectric constant of clean ballast. The results obtained are analyzed and the main conclusions are presented herein.<\/jats:p>","DOI":"10.3390\/rs6109712","type":"journal-article","created":{"date-parts":[[2014,10,14]],"date-time":"2014-10-14T02:13:08Z","timestamp":1413252788000},"page":"9712-9728","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":45,"title":["GPR Laboratory Tests For Railways Materials Dielectric Properties Assessment"],"prefix":"10.3390","volume":"6","author":[{"given":"Francesca","family":"De Chiara","sequence":"first","affiliation":[{"name":"Sapienza University of Rome, Via Eudossiana 18, 00184 Rome, Italy"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-0266-4305","authenticated-orcid":false,"given":"Simona","family":"Fontul","sequence":"additional","affiliation":[{"name":"National Laboratory for Civil Engineering (LNEC), Avenida do Brasil, 101, 1700-066 Lisbon, Portugal"}]},{"given":"Eduardo","family":"Fortunato","sequence":"additional","affiliation":[{"name":"National Laboratory for Civil Engineering (LNEC), Avenida do Brasil, 101, 1700-066 Lisbon, Portugal"}]}],"member":"1968","published-online":{"date-parts":[[2014,10,13]]},"reference":[{"key":"ref_1","unstructured":"INNOTRACK: Concluding Technical Report. Available online: http:\/\/www.innotrack.net\/IMG\/pdf\/innotrack_concl_20techn_report_lowres.pdf."},{"key":"ref_2","unstructured":"Modern Railway Track. Available online: http:\/\/www.esveld.com\/MRT_Selection.pdf."},{"key":"ref_3","unstructured":"Track Compendium: Formation, Permanent Way, Maintenance, Economics. Available online: http:\/\/www.eurailpress.de\/leseprobe\/148\/download\/magazine.pdf."},{"key":"ref_4","doi-asserted-by":"crossref","unstructured":"Selig, E.T., and Waters, J.M. (1994). Track Geotechnology and Substructure Management, Thomas Telford.","DOI":"10.1680\/tgasm.20139"},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"463","DOI":"10.1016\/S0963-8695(99)00025-0","article-title":"The application of time domain ground penetrating radar to evaluate railway track ballast","volume":"32","author":"Gallagher","year":"1999","journal-title":"NDT E Int"},{"key":"ref_6","unstructured":"Manacorda, G., Morandi, D., Sarri, A., and Staccone, G. (May, January 29). Customized GPR system for railroad track verification. Santa Barbara, CA, USA."},{"key":"ref_7","unstructured":"Topping, Y. (2011, January 6\u20139). Non-destructive tests for railway infrastructure stiffness evaluation. Chania, Crete. Paper 16."},{"key":"ref_8","unstructured":"Hyslip, J.P., Chrismer, S., LaValley, M., and Wnek, J. (2012, January 16\u201319). Track quality from the ground up. Chicago, IL, USA."},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"145","DOI":"10.1016\/S0963-8695(02)00053-1","article-title":"Evaluation of railway trackbed and formation: A case study","volume":"36","author":"Brough","year":"2003","journal-title":"NDT E Int"},{"key":"ref_10","unstructured":"Fontul, S. (2004). Structural Evaluation of Flexible Pavements Using Non-Destructive Tests. Ph.D. Thesis, Departamento de Engenharia Civil, Universidade de Coimbra, Coimbra, Portugal."},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"457","DOI":"10.1016\/S0963-8695(99)00023-7","article-title":"Imaging attributes of railway track formation and ballast using ground probing radar","volume":"32","author":"Jack","year":"1999","journal-title":"NDT E Int"},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"147","DOI":"10.1016\/S0926-9851(99)00054-3","article-title":"Railway track inspection using GPR","volume":"43","author":"Hugenschmidt","year":"2000","journal-title":"J. Appl. Geophys"},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"157","DOI":"10.1016\/S0963-8695(02)00054-3","article-title":"Railway track condition indicators from ground penetrating radar","volume":"36","author":"Sussmann","year":"2003","journal-title":"NDT E Int"},{"key":"ref_14","unstructured":"Smekal, A., Berggren, E.G., and Silvast, M. (2006, January 5\u20137). Monitoring and substructure condition assessment of existing railway lines for upgrading to higher axle loads and speeds. Montreal, QC, Canada."},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"309","DOI":"10.1080\/10298431003749741","article-title":"Inspection of railroad ballast using geophysical method","volume":"11","author":"Plati","year":"2010","journal-title":"Int. J. Pavement Eng"},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"345","DOI":"10.1243\/09544097JRRT367","article-title":"An inspection of railway ballast quality using ground penetrating radar in Finland","volume":"224","author":"Silvast","year":"2010","journal-title":"Proc. Inst. Mech. Eng. Part F J. Rail Rapid Transit"},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"305","DOI":"10.1016\/S0963-8695(00)00006-2","article-title":"Electromagnetic properties of railway ballast","volume":"34","author":"Clark","year":"2001","journal-title":"NDT E Int"},{"key":"ref_18","unstructured":"Fortunato, E. (2005). Renova\u00e7\u00e3o de Plataformas Ferrovi\u00e1rias. Estudos Relativos \u00e0 Capacidade de Carga. Ph.D. Thesis, Departamento de Engenharia Civil, Porto, Faculdade de Engenharia da Universidade do Porto, Porto, Portugal."},{"key":"ref_19","unstructured":"Saarenketo, T. (2006). Electrical Properties of Road Materials and Subgrade Soils and the Use of Ground Penetrating Radar in Traffic Infrastructure Surveys. Ph.D. Thesis, Faculty of Science, University of Oulu, Oulu, Finland."},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"55","DOI":"10.3208\/sandf.50.55","article-title":"Characterization of the fouled ballast layer in the substructure of a 19th century railway track under renewal","volume":"50","author":"Fortunato","year":"2010","journal-title":"Soils Found"},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"322","DOI":"10.1139\/T10-066","article-title":"A new parameter for classification and evaluation of railway ballast fouling","volume":"48","author":"Indraratna","year":"2011","journal-title":"Can. Geotech. J"},{"key":"ref_22","doi-asserted-by":"crossref","unstructured":"Zhang, Q., Gascoyne, J., and Eriksen, A. (2011, January 29\u201330). Characterisation of ballast materials in trackbed using ground penetrating radar: Part 1. Derby, UK.","DOI":"10.1049\/cp.2011.0593"},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"175","DOI":"10.1016\/j.jappgeo.2011.05.002","article-title":"Model track studies on fouled ballast using ground penetrating radar and multichannel analysis of surface wave","volume":"74","author":"Anbazhagan","year":"2011","journal-title":"J. Appl. Geophys"},{"key":"ref_24","unstructured":"De Chiara, F. (2014). Improving of Railway Track Diagnosis Using Ground Penetrating Radar. Ph.D. Thesis, Sapienza University of Rome, Rome, Italy."}],"container-title":["Remote Sensing"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/2072-4292\/6\/10\/9712\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,11]],"date-time":"2025-10-11T21:16:48Z","timestamp":1760217408000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/2072-4292\/6\/10\/9712"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2014,10,13]]},"references-count":24,"journal-issue":{"issue":"10","published-online":{"date-parts":[[2014,10]]}},"alternative-id":["rs6109712"],"URL":"https:\/\/doi.org\/10.3390\/rs6109712","relation":{},"ISSN":["2072-4292"],"issn-type":[{"value":"2072-4292","type":"electronic"}],"subject":[],"published":{"date-parts":[[2014,10,13]]}}}