Combined InSAR and Terrestrial Structural Monitoring of Bridges

This paper examines advances in InSAR satellite measurement technologies to understand their relevance, utilisation and limitations for bridge monitoring. Waterloo Bridge is presented as a case study to explore how InSAR data sets can be combined with traditional measurement techniques including sensors installed on the bridge and automated total stations. A novel approach to InSAR bridge monitoring was adopted by the installation of physical reflectors at key points of structural interest on the bridge, in order to supplement the bridge’s own reflection characteristics and ensure that the InSAR measurements could be directly compared and combined with insitu measurements. The interpretation and integration of InSAR data sets with civil infrastructure data is more than a trivial task, and a discussion of uncertainty of measurement data is presented. Finally, a strategy for combining and interpreting varied data from multiple sources to provide useful insights into each of these methods is presented, outlining the practical applications of this data analysis to support wider monitoring strategies.Author funding under EPSRC (UK) Award 1636878, co-author funding under Research Council of Norway (RCN Grant no. 237906)

An integrated investigative approach in health monitoring of masonry arch bridges using GPR and InSAR technologies

This paper provides an overview of the existing health monitoring and assessment methods for masonry arch bridges. In addition, a novel “integrated” holistic non-destructive approach for structural monitoring of bridges using ground-based non-destructive testing (NDT) and the satellite remote sensing techniques is presented. The first part of the paper reports a review of masonry arch bridges and the main issues in terms of structural behaviour and functionality as well as the main assessment methods to identify structural integrity-related issues. A new surveying methodology is proposed based on the integration of multi-source, multi-scale and multi-temporal information collected using the Ground Penetrating Radar (GPR – 200, 600 and 2000 MHz central-frequency antennas) and the Interferometric Synthetic Aperture Radar (InSAR – C-band SAR sensors) techniques. A case study (the “Old Bridge” at Aylesford, Kent, UK – a 13th century bridge) is presented demonstrating the effectiveness of the proposed method in the assessment of masonry arch bridges. GPR has proven essential at providing structural detailing in terms of subsurface geometry of the superstructure as well as the exact positioning of the structural ties. InSAR has identified measures of structural displacements caused by the seasonal variation of the water level in the river and the river bed soil expansions. The above process forms the basis for the “integrated” holistic structural health monitoring approach proposed by this paper

Development of an unsupervised remote sensing methodology of detect surface leakage from terrestrial CO2 storage sites

Imperial Users onl

Evaluating the benefit of structural health monitoring for improving bridge resilience against scour. Deliverable D1 – Report on critical review of alternative techniques for bridge scour monitoring

No abstract available

Developing Advanced Photogrammetric Methods for Automated Rockfall Monitoring

[eng] In recent years, photogrammetric models have become a widely used tool in the field of geosciences thanks to their ability to reproduce natural surfaces. As an alternative to other systems such as LiDAR (Light Detection and Ranging), photogrammetry makes it possible to obtain 3D points clouds at a lower cost and with a lower learning curve. This combination has allowed the democratisation of this 3D model creation strategy. On the other hand, rockfalls are one of the geological phenomena that represent a risk for society. It is the most common natural phenomenon in mountainous areas and, given its great speed, its hazard is very high. This doctoral thesis deals with the creation of photogrammetric systems and processing algorithms for the automatic monitoring of rockfalls. To this end, 3 fixed camera photogrammetric systems were designed and installed in 2 study areas. In addition, 3 different workflows have been developed, two of which are aimed at obtaining comparisons of higher quality using photogrammetric models and the other focused on automating the entire monitoring process with the aim of obtaining automatic monitoring systems of low temporal frequency. The photogrammetric RasPi system has been designed and installed in the study area of Puigcercós (Catalonia). This very low-cost system has been designed using Raspberry cameras. Despite being a very low-cost and low-resolution system, the results obtained demonstrate its ability to identify rockfalls and pre-failure deformation. The HRCam photogrammetric system has also been designed and installed in the Puigcercós study area. This system uses commercial cameras and more complex control systems. With this system, higher quality models have been obtained that enable better monitoring of rockfalls. Finally, the DSLR system has been designed similarly to the HRCam system but has been installed in a real risk area in the Tajo de San Pedro in the Alhambra (Andalusia). This system has been used to constantly monitor the rockfalls affecting this escarpment. In order to obtain 3D comparisons with the highest possible quality, two workflows have been developed. The first, called PCStacking, consists of stacking 3D models in order to calculate the median of the Z coordinates of each point to generate a new averaged point cloud. This thesis shows the application of the algorithm both with ad hoc created synthetic point clouds and with real point clouds. In both cases, the 25th and 75th percentile errors of the 3D comparisons were reduced from 3.2 cm to 1.4 cm in synthetic tests and from 1.5 cm to 0.5 cm in real conditions. The second workflow that has been developed is called MEMI (Multi-Epoch and Multi-Imagery). This workflow is capable of obtaining photogrammetric comparisons with a higher quality than those obtained with the classical workflow. The redundant use of images from the two periods to be compared reduces the error to a factor of 2 compared to the classical approach, yielding a standard deviation of the comparison of 3D models of 1.5 cm. Finally, the last workflow presented in this thesis is an update and an automation of the method for detecting rockfalls from point-clouds carried out by the RISKNAT research group. The update has been carried out with two objectives in mind. The first is to transfer the entire working method to free licence (both language and programming), and the second is to include in the processing the new algorithms and improvements that have recently been developed. The automation of the method has been performed to cope with the large amount of data generated by photogrammetric systems. It consists of automating all the processes, which means that everything from the capture of the image in the field to the obtention of the rockfalls is performed automatically. This automation poses important challenges, which, although not completely solved, are addressed in this thesis. Thanks to the creation of photogrammetric systems, 3D model improvement algorithms and automation of the rockfall identification workflow, this doctoral thesis presents a solid and innovative proposal in the field of low-cost automatic monitoring. The creation of these systems and algorithms constitutes a further step in the unimpeded expansion of monitoring and warning systems, whose ultimate goal is to enable us to live in a safer world and to build more resilient societies to deal with geological hazards.[cat] En els darrers anys, els models fotogramètrics s’han convertit en una eina molt utilitzada en l’àmbit de les geociències gràcies a la seva capacitat per reproduir superfícies naturals. Com a alternativa a altres sistemes com el LiDAR (Light Detection and Ranging), la fotogrametria permet obtenir núvols de punts 3D a un cost més baix i amb una corba d’aprenentatge menor. Per altra banda, els despreniments de roca són un dels fenòmens geològics que representen un risc per al conjunt de la societat. Aquesta tesi doctoral aborda la creació de sistemes fotogramètrics i algoritmes de processat per al monitoratge automàtic de despreniments de roca. Per una banda, s’ha dissenyat un sistema fotogramètric de molt baix cost fent servir càmeres Raspberry Pi, anomenat RasPi System, instal·lat a la zona d’estudi de Puigcercós (Catalunya). Per altra banda, s’ha dissenyat un sistema fotogramètric d’alta resolució anomenat HRCam també instal·lat a la zona d’estudi de Puigcercós. Finalment, s’ha dissenyat un tercer sistema fotogramètric de manera similar al sistema HRCam anomenat DSLR, instal·lat en una zona de risc real al Tajo de San Pedro de l’Alhambra (Andalusia). Per obtenir comparacions 3D amb la màxima qualitat possible, s’han desenvolupat dos fluxos de treball. El primer, anomenat PCStacking consisteix a realitzar un apilament de models 3D per tal de calcular la mediana de les coordenades Z de cada punt. El segon flux de treball que s’ha desenvolupat s’anomena MEMI (Multi-Epoch and Multi-Imagery). Aquest flux de treball és capaç d’obtenir comparacions fotogramètriques amb una qualitat superior a les que s’obtenen amb el flux de treball clàssic. Finalment, el darrer flux de treball que es presenta en aquesta tesi és una actualització i una automatització del mètode de detecció de despreniments de roca del grup de recerca RISKNAT. L’actualització s’ha dut a terme perseguint dos objectius. El primer, traspassar tot el mètode de treball a llicència lliure (tant llenguatge com programari) i el segon, incloure els nous algoritmes i millores desenvolupats en aquesta tesi en el processat fotogramètric Gràcies a la creació dels sistemes fotogramètrics, algoritmes de millora de models 3D i l’automatització en la identificació de despreniments aquesta tesi doctoral presenta una proposta sòlida i innovadora en el camp del monitoratge automàtic de baix cost. La creació d’aquests sistemes i algoritmes representen un avenç important en l’expansió dels sistemes de monitoratge i alerta que tenen com a objectiu final permetre'ns viure en un món més segur i construir societats més resilients enfront dels riscos geològics

High resolution anatomical and functional imaging

The signal-to-noise ratio available in Magnetic Resonance Imaging (MRI)is determined by the static magnetic field strength, causing a continued drive toward higher fields to enable faster image acquisition at finer spatial resolution. The work in this thesis is primarily concerned with the development of sequences for Ultra High Field Magnetic Resonance Imaging (7T) which allow the acquisition of images with high spatial resolution for study of the structure and function of the brain. The methods developed here for high spatial resolution structural imaging allow the identification of regions of the cortex which exhibit layers of high myelin concentration within the cortical strip. This permits the investigation of the correspondence of functional regions in the visual cortex to their underlying structure 'in vivo'. A robust methodology for high resolution functional mapping over a restricted field of view is presented and the results of fMRI studies demonstrating 1 mm isotropic resolution in the primary somatosensory cortex S1 using this methodology are shown. BOLD responses to vibrotactile digit stimulation were investigated using a travelling wave paradigm to measure the topographic representation of the digits in S1 and an event related paradigm for characterization of the haemodynamic delay. A spin-echo EPI acquisition has been optimized and tested to compare the BOLD response in GE and SE echo planar images by employing visual and motor tasks. The specificity of the BOLD responses of SE and GE data was found to be similar using a travelling wave paradigm

The role of carbon nanotube structure in their retention and pathogenicity in the pleural cavity

Carbon nanotubes (CNT) are hexagonal arrangements of carbon atoms built up to form fibres with diameters in the nanometre range but lengths which may extend up to hundreds of microns. The physiochemical properties of CNT are advantageous for a variety of industrial applications leading to CNT becoming one of the major products in the burgeoning field of nanotcchnology. However their structural similarity to asbestos has raised concerns that they may also pose an occupational inhalation hazard and cause diseases of the lung or pleura. Several decades of fibre toxicology have lead to the development of a robust structure/activity model, the fibre pathogenicity paradigm (FPP), which identifies length, thinness and biopersistence as the critical properties a fibrous particle must possess if it is to be pathogenic. The purpose of this study was to examine the pathogenicity of CNT in relation to the FPP by examining the effect of CNT in the pleural space, a target tissue for asbestosrelated disease.In order to address this aim a method of injection directly into the pleura cavity of mice was employed. Direct instillation of long and short CNT into the pleural cavity produced length-dependent responses characterized by acute inflammation leading to progressive fibrosis on the parietal pleura which mirrored the pleura response to asbestos. Furthermore examination of the size-restricted clearance mechanisms from the pleural cavity confirmed the hypothesis that the pathogenicity of long CNT and other fibres, arises as a result of length-dependent retention at the stomata on the parietal pleura.The cellular interactions leading to an inflammatory response in the pleural cavity were also examined in an in vitro study which tested the CNT for their ability to stimulate the release of the acute phase cytokines from both mesothelial cells and macrophages. Direct exposure to CNT resulted in significant cytokine release from the macrophages but not mesothelial cells. This pro-inflammatory response was length dependent but modest and was shown to be a function of frustrated phagocytosis. Furthermore the indirect actions of the CNT were examined by treating the mesothelial cells with conditioned media from CNT-treated macrophages. This resulted in dramatic amplification of cytokine release from the mesothelial cells. We therefore hypothesise that long fibres elicit an inflammatory response in the pleural cavity via frustrated phagocytosis in pleural macrophages. The activated macrophages then stimulate an amplified pro-inflammatory cytokine response from the adjacent pleural mesothelial cells.A further aim was to investigate the relationship between the length-dependent pathogenicity of a fibre sample and the surface of the fibre. By using different forms of functional groups attached to the surface of a pathogenic CNT we tested if the level of inflammation and fibrosis triggered in vivo can be altered by simple alteration of the surface. Our results showed that, although the surface modification of CNT did not alter the acute inflammogenicity of the CNT, the chronic fibrotic response was significantly attenuated. The specific role surface chemistry played in the modification of the CNT pathogenicity however was obfuscated by the apparent lack of biopersistcncc of the functionalised CNT compared with the pristine sample.Although direct injection into the pleural space is a convenient model to assess the hazard of fibres to the mesothelium it is not a physiologically relevant route by which workers may be exposed to CNT. Therefore we examined the inflammatory potential of CNT on the lungs and pleural cavity following pharyngeal aspiration into the airspaces. A length-dependent inflammatory response in the lungs was observed where only the long CNT sample caused acute neutrophilic inflammation at one week and progressive interstitial thickening of the alveolar septa by six weeks post exposure. Furthermore we report the induction of a length-dependent inflammatory response in the pleural cavity after exposure to CNT via the lung airspaces with concomitant evidence for the translocation of CNT from the lung into in the pleural cavity and subsequent retention along the parietal pleura.In summary the results presented here demonstrate the length-dependent pathogenicity of CNT in the pleural cavity and highlights the necessity for risk assessment for people likely to be exposed in the workplace. We also explored mechanistic aspects of the inflammatory response to long CNT which has implications for the general understanding of fibre-related pleural disease and may prove useful for the design of safe nanofibres