Ground-penetrating radar (GPR) has been widely used in investigations of contaminated areas because of its sensitivity to variations associated with the nature of pore fluids. However, most of the studies were usually based on the visual interpretation of radargrams or on a time domain amplitude analysis. In this work, we propose a methodology that consists of analyzing the spectral content of the signal recorded in multi-frequency 3D GPR profiles. A remarkable advantage of this type of antenna is its step-frequency system, which provides a much wider emission spectrum than the one corresponding to conventional single-frequency antennas. From the data in the frequency domain, the dominant frequency and bandwidth were calculated as parameters whose variation could be related to the presence of light non-aqueous phase liquid (LNAPL) in the subsurface. By analyzing the variations of these two parameters simultaneously, we were able to delimit the contaminated zones in a case study, associating them with a significant shift of the frequency spectrum with respect to the average of the study area. Finally, as a validation method of the proposed methodology, the results of the frequency analysis were compared with resistivity data obtained with an electromagnetic conductivity meter, showing a very good correlation between the results.

Ground penetrating radar (GPR) is routinely used to locate the isolated elements that produce reflection hyperbolas in radargrams. However, we propose a method in this study for locating the various interfaces appearing in a medium by studying the signal attenuation to obtain resistivity sections. GPR signal decay has a strong relationship with the electromagnetic properties of the medium, particularly the electrical resistivity and permittivity. To assign values of resistivity to different layers, a relationship between the attenuation coefficient and the above parameters must be used. Moreover, there are geometric effects that affect the energy loss and, therefore, the signal amplitude, that are jointly considered for the elimination of such effects before calculating the attenuation coefficient. An envelope function of the traces previously corrected for geometric effects was created to detect interfaces in the medium and generate a local decay curve and radargram zonation. Two relationships are necessary for obtaining the resistivity values from signal decay: first, a relationship between the resistivity and relative permittivity of the medium; and second, a relationship between the attenuation coefficient and resistivity. A resistivity section obtained from the GPR data is shown with an electrical tomography section at the same location.

This study first reviews the influence of grain size on the permeability of porous granular media in comparison to other factors, especially the sorting of grain size distribution, in order to improve the physical knowledge of permeability. The aim of this research is to counter the widespread misconception that the characteristics of water flow in granular porous media can be associated exclusively with an area regarding grain size. This review involves two different aspects. First, the dependence of the intrinsic permeability on the particle size distribution is highlighted, independently of the other internal factors such as porosity and average grain size, by simply reviewing the main existing formulas. Second, the historical literature on the influence of the average grain size in porosity is analyzed, and it is compared with the influence of the granulometric sorting. The most recognized data show that the influence of each of these two factors is of the same order, but it was not expressed in mathematical form, so a relationship of porosity versus average grain size and sorting is established. The two aforementioned steps conclude that the factors influencing permeability do not advise the use of area dimensions because it leads to only link permeability with the average grain size, especially when nonspecialists come into contact with earth sciences. Finally, after a review of the historical evolution of the permeability units, they are redefined to avoid the common misconception that occurs when the established unit leads to only a partial understanding of the key parameters influencing permeability.

La prospección geofísica mediante georradar permite la identificación de ciertos elementos o estructuras presentes en el subsuelo, con gran rapidez y un alto grado de resolución. Es por ello, que el objetivo general planteado en esta tesis consiste en el análisis de las propiedades electromagnéticas del medio a partir de datos de georradar, mediante el planteamiento de tres objetivos específicos orientados al análisis cuantitativo y numérico de las señales. El primer objetivo propuesto consiste en el desarrollo de herramientas que permitan el estudio de pavimentos asfálticos mediante el análisis de la señal de georradar y más concretamente en la caracterización automática de capas y en el análisis del contenido de humedad. El segundo objetivo específico se centra en analizar los datos de georradar en el espectro de frecuencias para obtener la frecuencia dominante y el ancho de banda como índices que se pueden relacionar con la presencia de ciertos contaminantes en el medio investigado. El tercer y último de los objetivos definidos consiste en el desarrollo de un método experimental que permita obtener valores de permitividad eléctrica, por la importancia de este parámetro en la determinación de la velocidad de propagación de las señales de georradar. Los estudios derivados del análisis de la señal de georradar para la evaluación de pavimentos asfálticos han demostrado que, a partir de la comparación de amplitudes mediante el coeficiente de correlación de Pearson, junto con otros criterios basados en la información contenida en la curva envolvente y en los datos procedentes de puntos de control, es posible obtener una caracterización automática de los reflectores de interés. Además, mediante el análisis del grado de atenuación de la señal de georradar se ha conseguido identificar en los radargramas aquellas zonas con alto contenido en humedad. Por otro lado, la metodología propuesta para la optimización del análisis del ancho de banda y de la frecuencia dominante ha permitido delimitar las zonas contaminadas en un caso de estudio, asociándolas a aquellas en las que se produce una variación notable con respecto al espectro de frecuencias promedio de los perfiles de georradar. En cuanto a las medidas realizadas con el analizador de impedancias, se ha conseguido cuantificar la influencia de la humedad y de la conductividad en los valores de la permitividad eléctrica del medio. Este parámetro resulta determinante para poder calcular la velocidad de propagación de las ondas electromagnéticas durante el proceso de atribución de profundidades en el ámbito de aplicación del georradar. Como conclusión general se puede afirmar que la interpretación cuantitativa de los datos de georradar debería reemplazar a la tradicional interpretación visual de los radargramas. Por ello, las diferentes metodologías propuestas en esta tesis resultan de especial interés para ciertas investigaciones, como la caracterización de zonas contaminadas o el análisis del grado de humedad. En lo referente a la metodología propuesta en el análisis de las aplicaciones del georradar para el estudio de pavimentos asfálticos, se ha conseguido desarrollar una herramienta que permite, por un lado, la delimitación de capas del firme de una carretera de forma automática y por otro, cuantificar la presencia de humedades en el mismo por su relación con la atenuación de las señales de georradar. En cuanto al análisis conjunto del ancho de banda y la frecuencia dominante, la metodología propuesta ha demostrado su capacidad para obtener rápidos resultados relacionados con la presencia de contaminantes en el subsuelo, que a su vez dependen directamente de la conductividad y del grado de atenuación del medio investigado. Finalmente, en relación a la determinación de la permitividad eléctrica a partir del analizador de impedancias, se puede destacar que el método experimental desarrollado ofrece una fuerte estabilidad en las medidas realizadas para un amplio rango de frecuencias. ABSTRACT Geophysical prospecting by GPR (ground penetrating radar) allows the identification of certain elements or structures present in the subsoil, with great quickness and a high degree of resolution. Therefore, the general objective of this thesis is the analysis of the electromagnetic properties of the medium from GPR data, by means of three specific objectives oriented to the quantitative and numerical analysis of the signals. The first proposed objective consists in the development of tools that allow the study of asphalt pavements through the analysis of the GPR signal and more specifically in the automatic characterization of the layers and in the analysis of the moisture content. The second specific goal focuses on analyzing the GPR data in the frequency spectrum to obtain the dominant frequency and bandwidth as parameters that can be related to the presence of certain contaminants in the investigated medium. The third and last of the defined aims consists of the development of an experimental method to obtain the dielectric permittivity values, due to the importance of this parameter in the determination of the propagation velocity of the GPR signals. The studies derived from the analysis of the GPR signal for the evaluation of asphalt pavements have shown that, from the comparison of amplitudes by means of the Pearson correlation coefficient, together with other criteria based on the information contained in the envelope curve and in the data from control points, it is possible to obtain an automatic characterization of the reflectors of interest. In addition, by analyzing...

The importance of empirical versus theoretical laws is a controversial issue in many scientific fields, the latter being generally accepted and the relevance of which is not discussed here. As in other areas, there are well-known theoretical and empirical formulas in geosciences that do not adequately represent the reality of a given phenomenon. Quantitative comparison of geophysical and petrophysical results with data from the other multiple fields that comprise the geosciences compels a high exigency to avoid discontinuities in existing relationships. However, the proposal of new empirical laws that more accurately reflect a given phenomenon is often considered insufficient to contradict existing formulas. The aim of this work is to defend the development of new empirical laws by showing that they constitute a true model of analysed behaviour if certain criteria are followed. This defence is especially needed when non-linearisable functions are required to fit the empirical data. To achieve this aim, this study shows the established algebraic function as a function of a single variable, whose main advantage is its application to phenomena of a geological nature that show two differentiated behaviours as the variable x is increased. A series of five examples of different phenomena related to geosciences is selected to demonstrate the level of accuracy that new empirical laws can reach in contrast to the widely accepted historical relationships.

El paro cardiaco es un problema que causa anualmente un gran número de muertes en todo el mundo. Sin embargo, una parada cardiaca es un estado potencialmente reversible si se inicia inmediatamente una reanimación cardiaca de calidad y se utiliza un desfibrilador externo automático. En general, los simuladores utilizados en los cursos de formación no permiten evaluar objetivamente la maniobra de reanimación cardiopulmonar (RCP). Normalmente, estos simuladores solo cuentan con realimentación sonora sobre la profundidad de las compresiones. Así, tanto los alumnos mientras practican como los instructores mientras valoran la maniobra, deben evaluar y corregir la reanimación guiados por lo que perciben a simple vista y no en base a información objetiva. En este trabajo, se ha desarrollado un simulador clínico con realimentación a tiempo real, con el que se pretende facilitar el aprendizaje y la evaluación objetiva de la maniobra de RCP impartida en cursos de formación. Larraga-García, Blanca; Malo Íñiguez, Inés; Rubio Bolívar, Francisco Javier; Quintana-Díaz, Manuel; Guitérrez, Álvaro