La sonorité de l’échappement joue un rôle significatif sur le confort acoustique des occupants, ainsi que sur le caractère du véhicule. L’étude proposée porte sur la problématique industrielle suivante : « Description et quantification de la transmission du son entre la bouche d’échappement et l’intérieur du véhicule ». Physiquement la transmission sonore entre l’échappement et l’intérieur du véhicule s’effectue en trois étapes : Propagation des ondes sonores de la canule à la surface extérieure du véhicule et conversion en énergie vibratoire (1) ; Le bruit structurel se propage de la peau extérieure du véhicule à l’habillage intérieur (2) ; La surface intérieure du véhicule rayonne de l’énergie dans l’air à l’intérieur (3). Dans l’état de l’art proposé, la méthode de sous-structuration vibro-acoustique Patch Transfer Functions (PTF) est considérée comme une alternative viable à la problématique proposée. Cependant, avant d’appliquer la méthode sur un véhicule complet, la problématique suivante devait être résolue : « Caractérisation expérimentale d’un sous-système par des mesures sur un système couplé ». Ce manuscrit propose une méthode originale pour mesurer des fonctions de transfert d’un système découplé, sur la base de la réponse d’un système couplé. En raison de la nature mal posée du problème inverse, une méthode originale de régularisation a été proposée. La méthode a été validée pas des essais numériques, puis par un test physique. / Exhaust noise has a significant impact on acoustic comfort and the sound identity of a vehicle brand. The present study focuses on the: “Description and quantification of the sound transmission from the exhaust outlet into the interior of a vehicle”. Physically the noise propagation from the exhaust pipe to the cabin consists of three steps: The sound waves propagate through the air from the exhaust outlet to the external skin of the vehicle (1); the external skin vibrates and transmits its vibration to the internal skin (2); the internal skin radiates sound in the passengers’ cabin (3). The Patch Transfer Functions method, which is based on the framework of dynamic substructuring, allows for the consideration of this complex problem as simpler subproblems that consist of subsystem interactions. Yet the application of the method to a full vehicle requires addressing the problem: “Characterization of Patch Transfer Functions of a subsystem by means of measurement on a coupled system”. This dissertation presents an original inverse method for the measurement of Patch Transfer Functions. In industrial structures, this in-situ characterization is generally the only possible measurement method. Yet, due to the ill posed nature of the problem, the inversion process is difficult. An original regularization method is proposed. The method is tested through numerical simulations, and is validated with an experimental setup.

: Les travaux présentés dans cette thèse traitent du contrôle de systèmes dynamiques soumis à des excitations harmoniques et transitoires en utilisant des absorbeurs de type Nonlinear Energy Sink (NES). Plusieurs aspects ont été développés : la conception et la réalisation d'un nouveau design pour le NES cubique, l'étude de la location et du transfert irréversible d'énergie sur un NES bistable et le développement d'un critère de conception pour un NES à Vibro-Impact (VI). Dans un premier temps, un critère de conception est proposé pour le NES à raideur cubique. Le design proposé est basé sur des ressorts coniques ou des ressorts à pas variable. Un mécanisme à raideur négative est aussi introduit pour supprimer la partie linéaire et avoir une raideur cubique pure. Dans un deuxième temps, le concept du NES est validé expérimentalement par des essais statiques et des essais dynamiques. Une analyse de sensibilité est aussi menée sur la longueur des ressorts précontraints, elle dénote parfois un état bistable de l'oscillateur. Ensuite, le NES bistable ainsi obtenu est étudié plus en détail. Ce type d'absorbeur s'avère être très robuste pour différents types d’excitation. Des études expérimentales sont aussi menées afin d'explorer le comportement dynamique. Enfin, un critère de conception est proposé pour le NES à Vibro-Impact. Des calculs analytiques détaillés sont proposés pour contrôler les vibrations sous différentes excitations. L'étude expérimentale montre une bonne cohérence avec les résultats théoriques. / The work presented in this thesis deals with the passive control of dynamics systems subjected to harmonic and transient excitations using a Nonlinear Energy Sink (NES). Several research aspects have been developed: design theory and experimental study of a novel NES, efficient Targeted Energy Transfer (TET) of bistable NES and design criteria for optimally tuned Vibro-Impact (VI) NES. Firstly, a design criterion intended to provide optimal nonlinear stiffness is proposed. Then a novel design of NES system yielding cubic stiffness with conical springs or variable pitch springs and negative stiffness mechanism is developed. Secondly, the experimental procedures for static and dynamic test are presented and applied to validate the concept of NES system. Then a sensitivity analysis is performed with respect to the pre-compressed length of springs. Thirdly, the optimal design of the above device with negative stiffness (termed as bistable NES) is studied. This type of NES is proved to work robustly for different types of excitation, and experimental study of semi-active control are explored. Finally, design criteria for optimally tuned VI NES are studied. Detailed analytical calculations of clearance to control the vibration under different excitations are proposed. A good correspondence between theoretical and experimental results is observed.

La prédiction des vibrations induites par un écoulement est essentielle dans la conception des conduits de nombreuses installations industrielles, en particulier dans l’industrie du gaz. Notre étude concerne la prévision du bruit et la vibration des conduits soumis à un écoulement turbulent à faible nombre de Mach. Notre objectif est de présenter une étude numérique et expérimentale permettant aux ingénieurs de mieux comprendre le couplage entre l’excitation aléatoire et le conduit pour deux géométries (circulaire ou rectangulaire). Une approche expérimentale est développée et utilisée pour valider les prévisions numériques. Deux cas sont étudiés : (i) un conduit droit sans singularité, où les modes acoustiques du conduit sont excités par une couche limite turbulente (TBL) et (ii) un conduit droit avec un diaphragme inséré en amont qui génère une source acoustique localisée. La contribution acoustique est déterminée soit par des méthodes de mesure d’interspectres, soit à l’aide des outils de mécanique des fluides numérique (CFD) et d’analogies aéroacoustiques. La réponse de la structure est estimée par une approche dite de « couplage faible » qui utilise des fonctions de transfert modale d’un conduit fini simplement appuyé. Les mesures conduiront à évaluer et suggérer des améliorations de modèles empiriques existants de densité interspectrale de puissance (CPSD) dans un contexte d’écoulements internes turbulents. Une analyse modale expérimentale d’un conduit rectangulaire finie est confrontée à des méthodes de calcul pour évaluer l’effet des conditions aux limites, du rayonnement acoustique et de l’amortissement aérodynamique. Le couplage fluide structure est analysé par la fonction de « joint acceptance » à la fois dans le domaine spatial et dans le domaine des nombres d’onde. L’excitation comprend à la fois les contributions acoustiques et hydrodynamiques à l’aide des CPSD exprimées sur la base des fonctions de cohérence de type Corcos, champ diffus et modes acoustiques d’ordre élevé. Enfin, les études numériques et expérimentales de cette thèse ont été utilisées pour développer un cadre d’étude et de modélisation du bruit et des vibrations dans les conduites, qui relie la dynamique des fluides, les modèles analytiques et empiriques à des techniques efficaces d’analyse aléatoire. / Pipeline and duct vibrations can cause a range of issues from unplanned shutdownsto decreased equipment life time. Thus, the prediction of flow-induced vibrations is essential in piping design in many industrial plants, especially, for Gas industry. This study deals with the prediction of pipe flow noise and vibration at low Mach number. We aim to present a numerical and experimental study which can offer engineers a better understanding of the coupling between random excitation and duct section for two geometries (circular or rectangular). An experimental facility and measurement approach is developed and used to validate numerical predictions. Two cases are investigated: (i) a straight duct with no singularity, duct acoustic modes are excited by the Turbulent Boundary Layer (TBL) and (ii) a straight duct with a diaphragm inserted upstream generating a localized acoustic source. The acoustic contribution is either measured via cross-spectra based methods or calculated using Computational Fluid Dynamics (CFD) and aeroacoustic analogies. The response of the structure is estimated via a ‘blocked’ approach using analytical modal Frequency Response Functions (FRFs) of a simply supported finite duct. Measurements will lead to evaluate and suggest improvements to existing Cross Power Spectral Density (CPSD) empirical models in a context of internal turbulent flows. Experimental modalanalysis of a finite rectangular duct are confronted to computational methods to assess the effect of the Boundary Conditions (BCs), the resistive damping from coupling with the internal acoustic medium and aerodynamic damping. The fluid-structure coupling is analyzed through the joint acceptance function both in the spatial and wave number domain. The excitation includes both the acoustic and hydrodynamic contributions using CPSD written on the basis of Corcos, Diffuse Acoustic Field (DAF) and acoustic duct mode coherence functions. Finally, the numerical and experimental studies in this thesis were used to develop a framework for studying and modelling pipe flow noise and vibration which links CFD, analytical and empirical models to efficient random analysis techniques.

L’identification des efforts vibratoires agissant sur les structures et la détection des défauts à partir des mesures opérationnelles sont des sujets importants dans des projets académiques et industriels. Le choix de l’outil ou de la méthode utilisée dépend de la bande de fréquences d'étude puisqu’il existe des approches appropriées pour chaque domaine fréquentiel. Une méthode énergétique appelée la méthode énergétique simplifiée (MES) est utilisée pour prédire la répartition de la densité d'énergie vibroacoustique en moyennes et hautes fréquences. L'objectif de ce mémoire est d'étendre cette méthode pour résoudre les problèmes vibro-acoustiques inverses pour identifier d'une part les sources de vibration et d'autre part pour détecter les défauts. La formulation MES inverse (IMES) est numériquement validée pour des systèmes continus basés sur le couplage tel que le cas d’un système comportant plusieurs plaques couplées et celui d’un système composé d’une cavité acoustique couplée avec une plaque. En plus, une nouvelle méthodologie numérique est proposée, pour étendre cet outil d'identification IMES pour la détection des défauts. Une analyse paramétrique est effectuée pour le cas d’un modèle présentant des défauts afin de tester la robustesse et l’efficacité de cette approche. Finalement, une étude expérimentale est effectuée pour valider la technique IMES à fin d'identifier et localiser les charges exercées pour plusieurs cas, et détecter les défauts. / The identification of inputs forces acting on structures and the detection of defects from operating measurement have been important topics in both academic and industrial projects. The choice of the used tool or method depends on the frequency band of study since there are appropriate approaches for each frequency domain. An energetic method so called the simplified energy method (MES) is used to predict the distribution of the vibro-acoustic energy density in the medium and high frequency band. The objective of this thesis is to extend this energy method to solve inverse vibro-acoustic problems and to identify the sources of vibrations on one hand and to detect the defects on the other hand. The inverse MES formulation (IMES) is numerically validated for continuous coupling-based systems such as the case of a system composed with several coupled plates and the case of a system composed of an acoustic cavity coupled with a plate. In addition, a new numerical methodology is proposed to extend this IMES identification tool for the detection of defects. A parametric analysis is performed in the case of plate with defects in order to test the robustness and the efficiency of this approach. Finally, an experimental study is carried out to validate the IMES technique to identify and locate the input loads for several scenarios, and detecting the defects.

[pt] Nesta Tese, o design robusto, com um modelo incerto de um sistema de vibro-impacto eletromecânico é feito. O sistema é composto de um carrinho, cujo movimento é aciondo por um motor de corrente contínua e um martelo embarcado neste carrinho. O martelo é ligado ao carrinho por um mola não linear e por um amortecedor linear, de modo que existe um movimento relativo entre eles. Uma barreira linear flexível, colocada fora do carrinho, restringe aos movimentos do martelo. Devido ao movimento relativo entre o martelo e a barreira, impactos podem ocorrer entre estes dois elementos. O modelo metemático desenvolvido para sistema leva em conta a influência do motor no comportamento dinâmico do sistema. Alguns parâmetros do sistema são incertos, tais como a rigidez e os coeficientes de amortecimento da barreira flexível. O objetivo da Tese é realizar uma otimização deste sistema eletromecânico com respeito a parâmetros de projeto, a fim de maximizar a potência de impacto sob a restrição de que a potência elétrica consumida pelo motor seja menor do que um valor máximo. Para escolher os parâmetros de projeto no problema de otimização, uma análise de sensibilidade foi realizada a fim de definir os parâmetros mais sensíveis do sistema. O problema de otimização é formulado no âmbito de otimização robusta, devido à presença de incertezas no modelo. As distribuições de probabilidades das variáveis aleatórias são construídas através do Princípio da Máxima Entropia e estatísticas da resposta estocástica do sistema são calculadas pelo método de Monte Carlo. O conjunto de equações não-lineares é apresentado, e um integrador temporal adaptado é desenvolvido. O problema de otimização não-linear estocástico com restrição é resolvido para diferentes níveis de incertezas e também para o caso determinístico. Os resultados são diferentes e isto mostra a importância da modelagem estocástica. / [en] In this Thesis, the robust design with a uncertain model of a vibro-impact eletromechanical system is done. The electromechanical system is composed of a cart, whose motion is excited by a DC motor (motor with continuous current), and an embarked hammer into this cart. The hammer is connected to the cart by a nonlinear spring component and by a linear damper, so that a relative motion exists between them. A linear flexible barrier, placed outside of the cart, constrains the hammer movements. Due to the relative movement between the hammer and the barrier, impacts can occur between these two elements. The developed model of the system takes into account the influence of the DC motor in the dynamic behavior of the system. Some system parameters are uncertain, such as the stiffness and the damping coefficients of the flexible barrier. The objective of the Thesis is to perform an optimization of this electromechanical system with respect to design parameters in order to maximize the impact power under the constraint that the electric power consumed by the DC motor is lower than a maximum value. To chose the design parameters in the optimization problem, a sensitivity analysis was performed in order to define the most sensitive system parameters. The optimization is formulated in the framework of robust design due to the presence of uncertainties in the model. The probability distributions of random variables are constructed using the Maximum Entropy Principle and statistics of the stochastic response of the system are computed using the Monte Carlo method. The set of nonlinear equations are presented, and an adapted time domain solver is developed. The stochastic nonlinear constrained design optimization problem is solved for different levels of uncertainties, and also for the deterministic case. The results are different and this show the importance of the stochastic modeling. / [fr] Dans cette Thèse, nous étudions l optimization robuste avec un modèle incertain d un système étrectromécanique avec vibro-impact. Le système életromécanique est contitué d un chariot dont le mouvement est généré par un moteur à courant continu, et d un mateau embarqué dans ce chariot. Le Marteau est relié au chariot par un resort non linéaire et par un amortisseur linéaire, de façon qu un mouvement relative existe entre eux. Une barrière flexible linéaire, placée à l extérieur du chariot limite les mouvements du Marteau. En raison du mouvement relative entre le Marteau et la barrière, des impacts peuvent se produire entre ces deux éléments. Le modèle du système dèveloppé prend en compte l influence du moteur à courant continu dans la comportement dynamique du système. Certains paramètres du système sont incertains, tells que les coefficients de rigidité et d amortissement de la barreire flexible. L objectif de la Thèse est de réaliser une optimization de ce système életromécanique en jouant sur les paramètres de conception. Le but est de maximizer la puissance d impact sous la contrainte que la puissance électrique consommée par le moteur à courant continu soit inférieure à une valeur maximale. Pour choisir les paramétres de conception dans le probléme d optimisation, une analyse de sensibilité a été réalisée afin de definir les paramètres du système les plus sensibles. L optimisation est formulée dans le cadre de la conception robuste em raison de la présence d incertitudes dans le modele. Les lois de probabilités des variables aléatoires du problème sont construites em utilisant le Principle du Maximum d Entropie. Les statistiques de la réponse stochastique du système sont caçculées em utilisant la méthode de Monte Carlo. L emsemble de équations non linéaires est presente, et um solveur temporel adapte est développé. Le probléme d optimisation non linéaire stochastique est résolu pour différents niveaux d incertitudes, ainsi que pour le cas déterministe. Les résultats sont différents, ce qui montre l importance de la modélisation stochastique.

La hiérarchisation de la puissance injectée par des sources acoustiques dans une cavité d'avion telle qu'un cockpit, en vol, revêt un caractère majeur dans le but d'en réduire le bruit intérieur. Afin de répondre à ce besoin, la nécessité de considérer la cavité dans son ensemble à l'aide d'une méthode globale se révèle importante. Au cours de cette thèse, une méthode d'identification basée sur une méthode énergétique locale, appelée MES pour Méthode Energétique Simplifiée, est utilisée. En connaissant la géométrie de la cavité, ainsi que l'absorption des matériaux qui la composent, elle permet de déterminer la puissance rayonnée par les différentes sources acoustiques à l'intérieur de la cavité, à l'aide de mesures d'intensité tridimensionnelle, et de densité d'énergie acoustique totale. Afin de tester la méthode dans un cas réel, mesurer ces quantités énergétiques s'avère alors nécessaire. Une sonde acoustique est donc conçue, fabriquée, testée et enfin validée. Basée sur quatre mesures de pressions réalisées autour d'une sphère rigide à l'aide de microphones électrostatiques déportés, elle permet de mesurer la pression et le vecteur vitesse particulaire au centre de la sphère, et d'en déduire alors l'intensité 3D et la densité d'énergie totale. Un démonstrateur est ensuite construit pour réaliser des essais. Il s'agit d'une maquette de cockpit basée sur celui de l'A380. Différents essais acoustiques et vibro-acoustiques permettent alors de démontrer la capacité de l'association formée par la méthode d'identification et la sonde à déterminer la puissance injectée par les différentes sources dans des conditions acoustiques plus ou moins sévères, avec une précision de l'ordre de 2dB. Le post-traitement à l'aide de la MES des flux acoustiques rayonnés ainsi déterminés permet également de reconstruire le champ acoustique dans la cavité, ainsi que de séparer les différentes contributions en des points d'intérêt tels que les têtes pilote et copilote. / Organizing into a hierarchy the power injected by acoustic sources inside an aircraft cavity such as a cockpit, in flight conditions, appears as a crucial stage in orcier to reduce interior noise. To address this need, considering the whole cavity with a global method turns out to be essential. In this work, an identification method based on a local energy method called MES for Simplified Energy Method is used. With the cavity geometry and the absorption characteristics of the materials inside, the method is capable of retrieving the acoustic power radiated by the sources within the cavity from three dimensional intensity vector and energy density measurements. To assess the method in a real test case, measuring these previous energy quantities turns out to be necessary. Thus, an acoustic probe is designed, manufactured, tested and to finish validated. Based on four pressure measurements performed around a hard sphere with remote pre-amplified microphones, the multi-sensor probe is able to compute the pressure and the particle velocity vector at the center of the sphere, and then obtain the 3D intensity, and the total acoustic energy density. A cockpit mock-up based on the A380 cockpit geometry is manufactured to perform tests. Several acoustic and vibro-acoustic tests carried out in the mock-up show the capability of the association composed of the identification method and the probe to extract the acoustic power radiated by the sources, in more or less harsh acoustic conditions, with accuracy close to 2dB. Post-processing the computed injected power allows to reconstruct the acoustic field inside the cavity, and to separate the different sources contributions for sorne points of interest such as the pilot or copilot heads.

The target of the research is to employ the autoresonant control technique in order to maintain the nonlinear oscillation mode at resonance (i.e. ultrasonic vibration at the tip of a drill bit at a constant level) during vibro-impact process. Numerical simulations and experiments have been executed. A simplified Matlab-Simulink model which simulates the ultrasonically assisted machining process consists of two parts. The first part represents an ultrasonic transducer that contains a piezoelectric transducer and a 2-step concentrator (waveguide). The second part reflects the applied load to the ultrasonic transducer due to the vibro-impact process. Parameters of the numerical models have been established based on experimental measurements and the model validity has been confirmed through experiments performed on an electromechanical ultrasonic transducer. The model of the ultrasonic transducer together with the model of the applied load was supplemented with a model of the autoresonant control system. The autoresonant control intends to provide the possibility of self-tuning and self-adaptation mechanism for an ultrasonic transducer to maintain its resonant regime of oscillations automatically by means of positive feedback. This is done through a signal to be controlled (please refer to Figure 7.2 and Figure 7.3) transformation and amplification. In order to examine the effectiveness and the efficiency of the autoresonant control system, three control strategies have been employed depending on the attributes of the signals to be controlled . Mechanical feedback control uses a displacement signal at the end of the 2nd step of the ultrasonic transducer. The other two control strategies are current feedback control and power feedback control. Current feedback control employs the electrical current flowing through the piezoceramic rings (piezoelectric transducer) as the signal to be controlled while power feedback control takes into account both the electrical current and the power of the ultrasonic transducer. Comparison of the results of the ultrasonic vibrating system excitation with different control strategies is presented. It should be noted that during numerical simulation the tool effect is not considered due to the complexity of a drill bit creates during the Ultrasonically Assisted Drilling (UAD) process. An effective autoresonant control system was developed and manufactured for machining experiments. Experiments on Ultrasonically Assisted Drilling (UAD) have been performed to validate and compare with the numerical results. Two sizes of drill bits with diameters 3mm and 6mm were applied in combination with three autoresonant control strategies. These were executed during drilling aluminium alloys with one fixed rotational speed associated with several different feed rates. Vibration levels, control efforts, feed force reduction were monitored during experiments. Holes quality and surface finish examinations supplement analysis of the autoresonant control results. In addition, another interesting research on the investigation of the universal matchbox (transformer) has been carried out. Introducing a varying air gap between two ferrite cores allows the optimization of the ultrasonic vibrating system, in terms of the vibration level, effective matchbox inductance, voltage and current level, phase difference between voltage and current, supplied active power etc (more details please refer to Appendix I).

The power plant and aerospace industries have been facing a huge loss, due to structural failure. The structural failure occurs due to the presence of the crack in it. Hence, it becomes necessary to monitor the structural health under operating condition. Most of the techniques, for structural health monitoring are used for a specific purpose. Some of these techniques require structure dismantling, which is very much expensive and time consuming. So the vibration based structural health monitoring is advantageous, compared to other techniques. Most of the vibration based Structural Health Monitoring (SHM) approaches, use linear vibration theory. But, these linear vibration based procedures, have inherently low sensitivity to crack. Since crack introduces nonlinearities in the system, their merits in damage detection need to be investigated for SHM. In this thesis, the problem is focused on studying nonlinear dynamics of cracked structures for Structural Health Monitoring. For this, simulations and experiments are performed. The new procedure for the simulation is developed using Matlab-Simulink. It uses the numerical approximation for dynamic compliance operators and a nonlinear model of cracks contact faces interaction to study the dynamic behaviour of the cracked bar. Furthermore, the finite element model of the cracked cantilever bar with crack- tip plasticity is developed and the dynamic behaviour of the elasto-plastic bar is studied. Additionally, numerous experiments are performed to study the dynamics of cantilever bar with the fatigue crack in it. The results from Matlab-Simulink simulation shows the distribution of higher harmonics generated along the bar length, as a function of distance from the crack. In finite element simulation, comparison is made between the resonance frequency of cracked cantilever bar with and without crack-tip plasticity. It is found that, there is decrease in resonance frequency of the cracked bar with cracked tip plasticity, when compared with the resonance frequency of cracked bar without crack-tip plasticity. This reduction in resonance frequency is due to the crack-induced plasticity near the crack tip which affects the overall stiffness of bar. In experiments, the response is measured at four different points on the cracked cantilever bar at a given resonant frequency of excitation at lower and higher vibration amplitude. For lower vibration amplitude, it is found that the response obtained near the vicinity of the crack shows the presence of higher harmonics of resonant frequency, which disappears in the response obtained far away from the crack. For higher vibration amplitude, it is found that the response obtained near the vicinity of the crack shows the presence of higher harmonics along with the low frequency component. This low frequency component causes modulation, which leads to the generation of side band frequencies near the resonant frequency. The occurrence of low frequency component and side band frequencies is due to the vibro-impact behaviour of crack. The amplitude of these side band frequencies and higher harmonics are reduced in the response obtained far away from the crack. This indicates that crack-induced nonlinearity has a localized effect on the dynamics of bar. It is also observed that the magnitude of low frequency component is proportional to the magnitude of resonant frequency of excitation. This indicates that crack behaves like a signal modulator, detector of low frequency component and amplifier as the magnitude of low frequency component is proportional to the magnitude of resonant frequency excitation. From the Matlab-Simulink simulation and experimental results, it is concluded that crackinduced nonlinearity affects the dynamic behaviour of the cracked bar significantly, which will be effective in structural health monitoring. Keywords: vibro-impact, crack, dynamic compliance, harmonics, modulator, detector, amplifier, crack-tip plasticity, resonance frequency, structural health monitoring.

Ground Improvement using vibro stone columns is gaining increasing acceptance on marginal soft clay sites as a sustainable foundation solution, particularly for lightly loaded low-rise structures supported by shallow, narrow footings. Most experience in this context however has been with widespread loads and use of the wet top-feed stone column technique, which has now been largely superseded, on environmental grounds, by the dry bottom-feed technique, and for which no significant published field trial data currently exists in deep soft clay deposits in the context of shallow, narrow footings. This research is therefore principally concerned with evaluating both the ground response to installation of partial depth vibro stone columns using the dry bottom-feed method in a deep moderately sensitive soft clay soil, together with the influence of parameters such as stone column spacing and length, founding depth within a thin surface 'crust', and also foundation shape on the performance of narrow footings subsequently constructed and subjected to incremental loading, over the installed stone columns, at the Bothkennar soft clay research site in Scotland. Comparisons are made with footings constructed within the surface 'crust' at Bothkennar without stone columns. Whilst stone columns were satisfactorily constructed with the dry bottom-feed technique at Bothkennar, it was evident that the vibroflot should not remain in the ground for longer than is necessary, in order to avoid excessive soil disturbance. For this reason construction of partial depth stone columns to a more uniform diameter, without construction of an 'end bulb', is advocated. Stress ratio was found to increase significantly with increasing length of stone column and also applied load, up to a maximum value of around 4.0. Moreover, for a trial footing founded at the base of the 'crust', stresses attracted by the columns were higher than all other columns where founding depth (level) was at shallower depth in the crust. A significant stress transfer was also measured beneath the toe of columns intentionally installed shorter than the minimum design length predicted by the Hughes and Withers (1974) approach at all iii applied loads, but not for columns equal to, or longer than minimum design length, confirming the predictions of this laboratory-based approach at the field scale. The stress measurements recorded by the field instrumentation demonstrate that the behaviour of the composite stone column-soil-foundation system is complex, with simultaneous and interdependent changes in pore pressures, soil stress ratios and resulting stiffness of both soil and columns. Whilst observed settlements exceeded those predicted, with larger foundation settlements observed at low applied loads over stone columns than at the same loading level in untreated ground, principally due to soil disturbance and accelerated consolidation effects during initial loading, at higher applied loadings however the stone columns significantly reduced the rate and magnitude of settlement compared to a foundation in the untreated 'crust'. It is therefore clear that the stone columns 'reinforced' the weak soil, providing a significantly increased factor of safety against bearing failure.

A cold extrusion process has been developed to tailor a porous structure from polymeric waste. The use of an extruder to manufacture acoustic materials from recycled waste is a novel idea and the author is not aware of any similar attempts. The extruder conveys and mixes the particulates with a reacting binder. The end result is the continuous production of bound particulates through which a controlled amount of carbon dioxide gas that is evolved during the reaction is used to give the desired acoustic properties. The cold extrusion process is a low energy consuming process that reprocesses the post manufacturing waste into new vibro-acoustic products that can be used to meet the growing public expectations for a quieter environment. The acoustical properties of the developed products are modelled using Pade approximation and Johnson-Champoux-Allard models. Applications for the developed products are widespread and include acoustic underlay, insulation and panels in buildings, noise barriers for motorways and railway tracks, acoustic insulation in commercial appliances and transport vehicles.