A model for predicting the response of a system composed of a fluid halfspace, overlying a porous ground layer, resting on an elastic halfspace, to incident plane waves, is developed to include further porous elastic layers within the ground. The dynamic properties of the porous elastic layers are modelled using a modified Biot formulation. Using the same boundary conditions a Fast Field algorithm for Layered Air Ground Systems (FFLAGS) is formulated to predict acoustic propagation and acoustic-seismic coupling in the model layered system due to a point source in a horizontally stratified atmosphere. This is a full wave solution. Results are compared to those of existing propagation prediction methods. FFLAGS has been used to predict (i) the effects of temperature gradients on short range propagation over an asphalt like surface, (ii) sensitivity of received sound pressure levels to ground parameters for various atmospheric conditions, and (iii) the influence of ground parameters on acoustic-seismic coupling. Predictions of acoustic surface waves in the presence of an upward refracting atmosphere using Creeping wave theory and the FFP method have been shown to agree. Dispersion equation based predictions of surface wave types have been assessed. It has been shown that the high velocity surface waves predicted by dispersion equation solutions on porous and elastic ground surfaces are not predicted to be excited by a point source. However several other surface wave modes have been predicted in layered systems, similar to those predicted in visco-elastic media. The influence of ground elasticity on received sound pressure levels is examined. Measurable effects of elasticity of the surface are predicted for low density materials, and measured over a low density polyester foam. Controlled experiments have been performed to study the effect of soil wetting on acoustic to seismic coupling. It is found that the observed effects can be modelled using FFLAGS.

The main focus of this research was to gain an understanding as to how waves propagate through structures. Lamb's Problem was studied on an isometric half plane, where numerical results were obtained. The calculated wavefronts for this problem were in agreement to the numerical results. When a distributed pressure is applied on an isometric half plane, after a long period of time, the wavefronts look as if a point force was applied on the half plane. Waves propagating through an orthotropic material were obtained numerically; it was found that Huygens' Principle cannot be used to calculate the wavefronts. The impact of spherical and cylindrical projectiles on glass plates was studied next. The waves introduced into the material were calculated using Finite Element Analysis, and compared to calculated wavefronts using Snell's Law, where they were found to be in agreement with one another. The effects of circular and square discontinuities were also studied, where a creeping wave that is produced after a wave propagates past a circular hole is explained. A sandwich beam was also modeled using FEA, where the wavefronts were obtained, and were found to be in agreement with calculated wavefronts. The displacement of the bottom layer of the sandwich beam was obtained numerically; it was found that the bending of the beam occurs at the same time as whether the middle layer is present or not.

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L’objectif de cette thèse était d’étudier la possibilité de compromissions électromagnétiques par le rayonnement des lignes d’énergie électrique. Nous nous sommes concentrés sur deux cas de figure. Le premier, à l’intérieur de bâtiments, concerne la technologie CPL « courant porteur en ligne ». Le second, en extérieur, sur un site industriel, porte sur la problématique de la propagation et du rayonnement de signaux caractéristiques d’un matériel industriel.Dans le premier cas, nous détaillons les mécanismes mis en jeu dans le rayonnement des câbles « basse tension » (BT) par la mesure et la modélisation. On distingue deux canaux de propagation. Le premier « filaire » correspond au canal usuel d’une liaison CPL entre deux modems. Le second est le canal « sans fil », qui correspond à la réception, aux bornes d’une antenne magnétique, d’une injection en mode différentiel sur 2 fils du câble. Ces deux types de canaux de propagation sont caractérisés expérimentalement, ce qui permet de déduire grâce à un logiciel les possibilités de décodage de l’information portée par le rayonnement compromettant. Dans le second cas, qui prend en compte les lignes « haute tension » (HT), nous considérons les fonctions de transfert successives du courant, associées à la propagation sur les lignes BT, au passage du transformateur BT/HT, puis à la propagation sur les lignes HT. Des modélisations ont été réalisées à l’aide du logiciel commercial EMTP, dont les résultats ont été comparés aux mesures expérimentales obtenues au cours de ce travail. Le rayonnement des lignes HT est abordé tant d’un point de vue théorique qu’expérimental. / The aim of this thesis was to study the possibility for power lines to emit compromising electromagnetic radiations. We focused on two cases. The first one was inside buildings, on PLC “Power Line Communication”. The second one was outside, on an industrial site, and about propagation and radiation of the characteristic signals produced by an industrial material.In the first case, we describe, measuring and modeling, the mechanisms involved in radiation cable Low Voltage (LV). There are two channels of propagation. The first is "wired" and the usual channel of a PLC link between two modems. The second channel is "wireless", which corresponds to the reception, across a magnetic antenna, of a differential injection of 2 lines of the cable. Both types of propagation channels are characterized experimentally, which enable us to deduced, using software, the decoding possibility of the information carried out by the compromising emanations.In the second case, considering "High Voltage" (HV) lines, we studies the successive transfer functions of the current associated with the spread on LV lines, crossing the transformer LV / HV, and then spreading on HV lines. Modelings were performed using commercial software EMTP. The results were compared with experimental measurements obtained during our study. HV lines radiations are discussed both from a theoretical and an experimental perspective.