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1st Conference on Geophysics for Infrastructure Planning Monitoring and BIM
- Conference date: September 8-12, 2019
- Location: The Hague, Netherlands
- Published: 08 September 2019
21 - 38 of 38 results
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Application Benefits of Using Downhole Magnetic Resonance and Wireline Geophysical Logging for Geotechnical Ground Investigation Projects
Authors D. Gartner and B. RiglerSummaryGeotechnical ground investigations in nearshore conditions requires a level of precision and accuracy in the determination of subsurface parameters that is more rigorous than most applications of geophysical logs. As such, these projects demand a wealth of measurements of the subsurface by geophysical means. In the following examples for detailed interpretation of wireline logging, geotechnical data and packer test results are presented with particular interest to benefits of the DMR method and the detailed log analysis the geotechnical industry. Expansive suite of wireline logs included DMR, optical and acoustic televiewer, orientated four arm caliper, gamma-gamma density, resistivity and acoustic methods, leading to an accurate understanding of the rock strength and geo-mechanical properties. DMR measurements provided continuous total porosity and pore-size distribution data. Permeability estimations were also performed using DMR Porosity and T2 distribution data, packer test derived, in-situ permeability results were used to refine estimated permeabilities. Ability to significantly lower construction related risk by facilitating identification and detailed description of weak zones justifies the use of wireline geophysical logging and particularly the DMR method more broadly in the construction and engineering sectors.
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Satellite Based Radar Technology for Asset Management During Large-Scale Transport Infrastructure Projects
Authors R. Frauenfelder, M. Vöge, A. Pfaffhuber, C. Hauser and A. LysdahlSummaryGround settlement and associated deformation of existing infrastructure is a major risk in urban development projects. Project owners in such areas have a responsibility to document and manage settlement records before, during and after construction works. Traditionally, land surveying has been the state-of-practice tool to provide settlement monitoring data. Modern radar interferometry provides the opportunity to drastically increase the number of monitored locations, while at the same time reducing expenses for traditional geodetic survey work. We illustrate this technology for a large urban railway development project near Oslo, the capital of Norway.
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Fibre-Optic Strain Sensing: Game Changer for (Urban) Seismic Surveying?
Authors C. Krawczyk, P. Jousset and T. ReinschSummaryNatural hazard prediction and efficient crustal exploration benefit from densely designed surveys. Seismological techniques provide ground-motion data, while active seismics aims at structural imaging and increasingly on physical properties determination. Dense networks exist on some volcanoes and in exploration plays, but not in urban areas where data acquisition is more challenging.
We demonstrate that dynamic strain determination is now possible with conventional fibre-optic cables deployed for telecommunication. This is a new tool for earthquake location or for crustal exploration using unexpected sources. Thereby, this method provides key records for understanding subsurface dynamics, especially in urban areas.
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Keynote - Fibre-Optic Distributed Sensing for Infrastructure Objects and Near-Surface Monitoring
More LessSummaryFibre-optic distributed acoustic sensing (DAS) has developed into a technology that has found application in many different scientific, engineering and industrial fields, where dynamic strain measurements are used to analyze the elasto-dynamic behaviour of an object or medium. Using a highly coherent laser source, a standard telecom-grade optical fibre, usually utilized for network data transmission, can be turned into an array with tens of thousands of virtual sensors. Many of the advanced analysis algorithms, such as feature extraction, or various forms of near-surface or subsurface imaging, machine learning or AI, require spatially and temporally well-sampled wave field recordings with fine sampling intervals and large spatial coverage. Such a type of data acquisition is only possible, if the individual sensors can be deployed cheaply on a large scale; and can be operated continuously without the need for power and data storage at each sensor location. Distributed fibre-optic sensing is a sensing technology that enables such pervasive sensor networks and provides continuous data streams of high resolution and coverage to feed real-time or offline analysis algorithms. We demonstrate such possibilities with a transport system infrastructure recording of train movement while obtaining earthquakes recordings and measuring near-surface conditions.
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Using GPR at Deutsche Bahn and First Steps in Merging the Results with BIM Models
Authors J. Wolf and D. HofmannSummaryThe number of applications for the GPR method at Deutsche Bahn has grown over the last decades. Besides monitoring the substructure under railway tracks, GPR is used to detect the build-up of civil engineering structures to complete building plans, it is used to detect pipes and drains not noted in the records, as well as to detect the remnants of suspected former buildings in future construction sides.
The advance of GPR to survey a large-scale area non-destructively allows its use to inspect train platforms quickly and completely to help experts with the planning of maintenance, reconstruction and upgrades. Possible obstacles for reconstruction works such as unknown pipes, steel beams, old foundations, voids or even parts of a former tunnel were detected in the platforms of a main train station using GPR. First steps are taken to compile the results of the survey into a BIM model of the station. The aim is to help the planner get a workable view over the abundance of information gained by the different crafts. Thus supporting the time planning and budgeting of the reconstruction project.
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Spectral Analysis of Vibrations of ITU TRIGA MARK-II Nuclear Research Reactor Building, Istanbul, Turkey
Authors M. Cakman, U. Harmankaya, B. Barutcu, P. Inci Kocak, A. Ilki and A. KaslilarSummaryWe examine the spectral properties of the vibrations of ITU TRIGA MARK-II nuclear research reactor building located at the Istanbul Technical University Ayazaga campus, Istanbul, Turkey. Istanbul is located in a seismically active region, where a large earthquake is expected. The building is for the first time equipped with sensors by a government-university-industry collaboration. We installed twelve tri-axial MEMS accelerometers to the three-story building for monitoring purposes. We estimated the basic dynamic characteristics of the building, namely, modal frequencies, translational and rotational modes, and the soil structure interaction of the building by spectral methods, using a recorded earthquake and continuous vibration data. Our results are in general in agreement with the results of numerical calculations based on simple clamped model and three dimensional finite element structural analysis model. The aim of the study, in long term, is to monitor the structural health of the reactor building and involve a rapid damage assessment system as well as the earthquake early warning system to the reactor control facility.
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Cross-Correlation Analysis of Surface Waves for Group and Phase Velocity Mapping along a 2D Seismic Profile
Authors K. Leontarakis, C. Orfanos and G. ApostolopoulosSummarySurface-Wave Analysis is widely adopted for estimating S-wave velocity of near-surface, a crucial parameter appearing in geotechnical standards. In this paper two different approaches are implemented and compared for the creation of pseudo-2D dispersion images of phase and group velocity through the analysis of multichannel cross-correlation (CC) of surface waves at a Test site. The surface wave travel time tomography approach can produce precise phase and group velocity maps, since the eikonal equation is used for the inversion of the automatic estimated phase and group delays. However, when sharp lateral variations are exist near surface, an average 1D reference phase velocity model is not adequate to properly estimate them, due to cycle skipping problems at high frequencies. The implementation of the common mid-point cross correlation approach results to smoother mapping of the velocity distribution, though sensitive to near surface variations, both on group and phase velocity. In that way, a more reliable 2D reference phase velocity model can be assigned to the first approach. Moreover, the 3D velocity dispersion imaging assists in defining specific problematic areas as well as frequency bands of possible significant higher mode interference, in order to be excluded from the 2D Vs inversion procedure.
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Assessment of Reservoir Embankment Dam Condition Using Field and Laboratory Geophysical Techniques
Authors S. Donohue, A. Trafford, D. Gunn, B. Dashwood, R. Swift, D. McKillen and D. LeemonSummaryThis extended abstract briefly discusses some initial results from an ongoing collaborative research project between University College Dublin, Queen’s University Belfast and the British Geological Survey as well as industry partners Aecom, Canal & River Trust and the Environment Agency. The project, funded by the Natural Environment Research Council (NERC), is investigating the application of geophysical techniques for improving flood defence management at a number of sites in Northern Ireland and England. The expanded abstract focuses on initial results from one case study, where a number of geophysical methods have been used to forensically examine the cause of a reservoir embankment leak. Although geophysical surveys can provide useful information in isolation, when used in conjunction, or calibrated, with relevant geotechnical properties, they can be valuable tools for assessing geotechnical infrastructure condition and for identifying possible seepage pathways through reservoir embankment dams.
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Keynote - Structural Health Monitoring Meets Ambient Noise Seismology
Authors C. Hadziioannou, J. Salvermoser, R. Steinmann, L. Marten and E. NiederleithingerSummaryHow can we harness the ambient vibrations that move the ground - and buildings - everywhere and all the time? I will discuss methods that use ambient seismic noise to characterize shallow subsurface structure. How can we track changes sensed by the seismic wavefield, related to water saturation and frozen ground?
Can we use these methods on buildings, bridges, larger civil structures, to continuously monitor the structural health status, and potentially detect the effects of damage? I will present results of studies that delve into these questions.
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Long-Term Monitoring of Slopes that Affect Transport Infrastructure
Authors J. Holmes, S. Donohue, J. Chambers, P. Wilkinson, P. Meldrum, D. Gunn, R. Swift, B. Dashwood, M. Kirkham, S. Uhlemann, D. Huntley and P. BobrowskySummarySlope failures on the transport network are a growing issue as populations continue to expand, putting increasing demand on aging infrastructure, much of which is already operating at full capacity. Monitoring of such slopes is therefore necessary to maintain the serviceability of transport infrastructure, mitigating against the large social, economic and environmental costs that would emerge in the result of slope failure. Near-surface geophysics is used increasingly for the assessment of the condition of transport infrastructure. Here, the use of Proactive Infrastructure Monitoring and Evaluation (PRIME) Electrical Resistivity Tomography, which allows for continuous, near-real time monitoring of subsurface moisture conditions, is assessed in terms of its applicability to monitoring both man-made embankments and natural slopes that affect transport infrastructure. Long-term monitoring data is presented for two field sites (Old Dalby, a railway embankment in Leicestershire, UK, and the Ripley landslide, a natural slope in British Columbia, Canada). Results demonstrate the sensitivity of electrical resistivity to changes in moisture content, which vary seasonally, and highlight the advantage of resistivity imaging for monitoring slope moisture dynamics over predictions based on rainfall data alone, providing information on the spatial aspects of slope hydrogeological regimes.
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Geoelectric Modelling of Near-Surface Resistivity Distribution for the Design of Windfarm Grounding Grids
More LessSummaryThe design of grounding system of windfarms and large solar plants, which can be in the order of a few kilometres size, requires deeper geoelectric models than the usual models developed for the design of a typical electrical substation. The average apparent resistivity curves of windfarms located at the Northeast of Brazil, in the states of Bahia and Rio Grande do Norte, reveal that, in general, ground resistivity is high at these sites, resulting in high grounding resistances for the windfarm towers.
In this study we propose the use of 1D geoelectric models built from the combination of two types of geophysical soundings - the traditional Wenner.array method, which provides resistivity distribution of the shallow ground, combined with the AMT – Audio Magnetotelluric Method, which can investigate the resistivity distribution of the upper few kilometers.
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Where Geophysics Meets Asphalt - Monitoring Roads Using Fibre Optics
Authors M. Devrez, J.A. Karabacak, O. Dowd, H. Veerman and J. SingerSummaryFibre optic sensing technologies, and in particular Fibre Bragg Gratings (FBGs), are enabling high precision and detailed mapping of strain in various structures by direct integration into the material layers. Here, embedding fibre optic sensor lines in asphalt has been demonstrated to detect miniscule changes in lateral strain due to vertical deformations of road construction layers, in response to the loads in real-time traffic conditions. The spatial and temporal resolution of the system allows for very detailed mapping of the deformations due to vehicle loads, including the extraction of the viscoelastic properties of the pavement and the rigidity characteristics of the underlayers. By continuous and/or periodic monitoring of the dynamic asphalt behaviour in response to controlled loads, the long-term changes in the near-surface properties due to material aging because of weather conditions or traffic loads can be extracted. Such detailed analysis can enable monitoring of large-scale assets, literally paving the way for a new approach to asset management of roads.
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Monitoring the Effect of Artificial Dune Construction Using Multiple Geophysical Methods
Authors F. Schaars and M. GroenSummaryIn the winter of 2014/2015, the Dutch coast near Petten was reinforced by the construction of a large artificial dune. The dune was constructed next to the old sea dike that did not meet the current safety requirements. Since 2013, the Hollands Noorderkwartier Water Board has been monitoring ground- and surface water data to describe the transient effects of the construction on the groundwater quantity and quality. To keep track of the changes, a range of monitoring methods are applied. In addition to head measurements and water quality samples in monitoring wells, we use different geophysical methods to describe the reference and the current situation. We will show the pros and cons of the different methods, and how the combination of the results of all methods will get us closer to understanding the hydrological system and the consequences of the construction of the artificial dune.
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Raspberry Shake Sensor Field Tests for Unstable Rock Monitoring
Authors M. Taruselli, D. Arosio, L. Longoni, M. Papini and L. ZanziSummaryIn this work, we evaluate the performance of the Raspberry Shake 3D (RS-3D) seismometer in estimating the resonance frequencies of unstable rock blocks. In this perspective, we compared this low-cost sensor with the Nanometrics Trillium Compact 20s to assess whether RS-3D is suitable for the development of reliable rock monitoring systems. We carried out surveys on eight rock compartments located both in the Northern Italy and in the Maltese archipelago. Ambient noise recordings have been processed by computing the mean amplitude spectra, the ratio between the Raspberry Shake spectra and the Trillium ones, and the Horizontal-to-Vertical Spectral Ratio. The obtained results show that the RS-3D performs according to the vendor specifications, with slight spectral differences with respect to the Nanometrics reference. Our preliminary tests reveal that the Raspberry Shake may be a reliable sensor for estimating the fundamental frequency of unstable rock blocks provided the HV peak occurs within the RS flat frequency response, and, because of its low-cost, may promote the deployment of denser seismic monitoring networks.
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Geological Characterization and Geomechanical Parameters Assessment Using Electrical Resistivity Tomography and Seismic Methods
Authors B. Benjumea, A. Gabàs, A. Macau, F. Bellmunt, J. Ripoll, J. Ledo and S. FiguerasSummaryA broad understanding of the subsoil characteristics is required to deal with uncertainty in the infrastructure planning phase or even in the diagnosis of infrastructure damage. In this work, electrical resistivity and seismic methods have been employed for lithological characterization and geomechanical parameters assessment. The study area is characterized by high variability in geotechnical characteristics due to complex lithology. For lithological discrimination, we have used a soft clustering method to combine the independently electrical and seismic derived models. The outputs of this integration process are zonal models that help to decrease interpretation uncertainties. From single seismic profiles, both Vp and Vs information is extracted allowing geomechanical parameters to be estimated. All this information is critical for assessing the variance and inhomogeneity of the subsoil characteristics. The methodology shown in this work can be used in the infrastructure planning phase as well as to ascertain the causes of detected damage on built infrastructures.
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Quantitative Subsurface Information of Athens Basin (Greece) Derived from Urban Gravity Measurements
Authors S. Dilalos and J.D. AlexopoulosSummaryA disastrous earthquake of the past (7th September 1999) was the reason for acquiring 1.122 urban gravity measurements in order to investigate and model the deeper subsurface of Athens city basin. The aim was to gather any additional quantitative subsurface information based on the gravity survey, such as the density distribution provided by the 3D density models and depths of potential anomaly sources. The standard corrections have been applied (drift, tide, latitude, free-air, Bouguer, terrain ones) along with an additional Building Correction that was calculated based on the urban characteristics. The isolation of the residual anomaly has been accomplished with the contribution of the Fourier filters and power spectrum analysis. The Euler deconvolution has been used in order to calculate the depth solutions of anomalous sources, based on the residual maps. These solutions seem to identify with several fault zones. Some of these zones have already been mapped or proposed (covered ones) but additionally some new zones have been revealed. The 3D density model of the area provides information about the geometry of the subsurface geological bodies that can also be related to the tectonic structures of Athens basin beneath the surface.
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Field-Scale Quality Control of Lime-Cement Pillar in Conductive Clay Using Electrical Resistivity Tomography
Authors P. Olsson, S. Rejkjær and T. DahlinSummaryGround improvement with lime-cement pillars is becoming increasingly common in the Nordic countries for exploitation of areas with poor stability. However, there is no non-destructive method for quality control of the ground improvement. Significant changes in the electrical properties after mixing of the binders make electrical resistivity tomography (ERT) a potential method. In connection with lime-cement pillar trials for the Västlänken project in Gothenburg, Sweden, a series of different single borehole ERT measurements were performed. Three cases are compared in this paper: untreated ground, treated uncured ground and treated cured ground. The raw data pseudosections show a significant general drop in resistivity between the untreated and treated uncured data sets, while the curing process increase the resistivity significantly close to the borehole. Full 3D inversions have been carried out for all three cases. In model space the cured pillar is still causing a clear increase in resistivity around the borehole, while the decrease between the untreated and uncured case is less obvious than in data space. With the large contrast between the untreated and the treated uncured in data space it was expected to be visible in model space, improved inversion methods and settings could help resolve this.
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The Automated Geoelectrical Data Processing Workflow of the PRIME Infrastructure Monitoring System
Authors P. Wilkinson, J. Chambers, P. Meldrum, C. Watson, C. Inauen, R. Swift and G. CurioniSummaryPRIME (PRoactive Infrastructure Monitoring & Evaluation) is a low-cost geoelectrical ground monitoring system developed by the British Geological Survey. It is designed to integrate with standardised technologies and information delivery platforms to provide remote, near real-time, volumetric monitoring of infrastructure earthworks condition, thereby aiding asset failure prediction and timely intervention. A key recent development has been the implementation of a fully automated data processing workflow to enable regular and timely delivery of information to end-users. It is a customisable procedure, which enables each monitoring objective to have its own combination of processing steps applied to its data. The standard workflow consists of: data filtering and quality assurance; motion sensing (under development); inverse image generation; property translation via petrophysical relationships; and image analysis. The flexible implementation of the workflow will allow for new processing steps to be incorporated as they are developed.
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