Development of new GPR methodologies for soil and cement concrete pavement assessment
The study of surface geology by means of Ground Penetrating Radar (GPR) can provide information about abrupt lateral changes in the terrain. The location ofthese changes is very useful in seismic nanozonation studies, since it allows determining a priori the sectors in which the meas ures should be...
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| Tipo de recurso: | tesis doctoral |
| Estado: | Versión publicada |
| Fecha de publicación: | 2021 |
| País: | España |
| Institución: | CBUC, CESCA |
| Repositorio: | TDR. Tesis Doctorales en Red |
| OAI Identifier: | oai:www.tdx.cat:10803/671504 |
| Acceso en línea: | http://hdl.handle.net/10803/671504 https://dx.doi.org/10.5821/dissertation-2117-345315 |
| Access Level: | acceso abierto |
| Palabra clave: | Àrees temàtiques de la UPC::Enginyeria civil 55 624 69 |
| Sumario: | The study of surface geology by means of Ground Penetrating Radar (GPR) can provide information about abrupt lateral changes in the terrain. The location ofthese changes is very useful in seismic nanozonation studies, since it allows determining a priori the sectors in which the meas ures should be intensified . The thesis analyzes the effect of changes in granulometry and com paction in the subsurface radar records . lt is observed that a greater heterogeneity of the terrain produces an increase in the background noise ofthe signa! (clutter) dueto the backscattering ofthe waves. The analysis of the amplitude ofthe incoherent signa!, determined in each A-sean by means ofthe average value obtained in a certain time window, makes it possible to obtain graphs ofthe amplitude ofthe background noise versus the position ofthe trace in the profile . The results clearlydefine the sectors in which the amplitude value increases, associating them with the existence of heterogeneous materiaIs in the most superficial zone of the subsoil. On the other hand, the analysis of the frequency content ofthe received radar signa! shows abrupt changes that are sometimes related to the increase in the clutter amplitude. However, at other times they do not appear , even though there is an increase in noise. To analyze the effect, a seasonal study was carried out in an area eros sed by underground streams , comparing the results in the dry season with the results in the rainy season . In temporal space, the underground streams could be detected thanks to the increase in clutter. The results were compared with those obtained by passive seismic . In the frequency space, greater changes in frequencywere observed in the rainy season, while in the dry season these changes only appeared in the records obtained in the area where there was one of the streams. lt was concluded, therefore, that the study of the amplitude s pectrum could be used to determine the presence ofwater and, in the case ofstreams, to differentiate between active streams and drychannels. These results are of great interest for the planning of trans port infrastructures. In the second part ofthe thesis, damage to transport infrastructure is analyzed. Specifically, on rigid pavements. Often these pavements built by using reinforced concrete slabs, are covered by an asphalt layer, either by design or dueto periodical restorations. The interna! cracks that are generated are not observed on the surface until very advanced stages. Severa! laboratory experiments and field case studies were proposed to determine the ability of the GPR to locate cracks, studying the effect ofthickness, depth and fill material. lt was observed that cracks of a size that allow them to be considered as incipient can be detected, although the length ofthe vertical crack could only be detected in the case of cracks already in an advanced state of damage (of great width) or filled with saturated sand or water. The decrease in the speed ofthe signal due to the presence ofwater allowed a higher resolution. The experimental results were compared and verified with field case studies, on real roads. Similar effects were observed although with a more limited resolution. Us ing com putational methods, the anomalies recorded in the radargrams were related and verified in most ofthe cases, both experimentally and in field studies, with different types of cracks. |
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