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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
1 - 20 of 38 results
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Keynote - Geophysics in Infrastructure - An Industry Perspective
Authors M. Brough and A. VerweerdSummaryThis keynote speech will show an industry perspective of the application of geophysics in infrastructure construction and asset management projects. Geophysics is uniquely placed in this industry due to its flexibility in different targets and scales. Several examples will be used to highlight the current state of affairs, including an outlook to further integrate geophysics into the civil engineering discipline.
With the increasing need for upgrading existing infrastructure and construction of new large scale infrastructure, the industry is looking to geophysics to manage and identify risks through non-destructive techniques, reducing the costs and impact of these large construction works through proper planning and integration of various data streams into a combined deliverable model.
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Time-Synchronized Geophysical Investigations in Denied GPS-Time Spaces
Authors A. Malehmir, L. Dynesius and T. SjölundSummaryWithout doubt much more can be done to utilize underground workings for site investigations. A few years ago, we realized this offered a unique opportunity with important applications and benefits of providing synchronized surveys in underground spaces using receivers typically used at the surface. However, technical limitations were hindrances. We have now been able to pioneer a prototype system that can provide accurate GPS-time (micro-second accuracy) to an array of various sensors placed in different tunnels and in different depth levels. The solution will be useful for any deep mines, tunneling industry and anywhere that a synchronized survey is needed but accurate timing is not available directly via satellites. The system does not need extensive cabling or accessibility to mine communication and operational facilities. It is a mobile system, transportable to underground workings using a couple of small boxes, and easy to set-up. Add-on options and modularity are also possible to provide greater flexibilities. Such a solution can bring for example 3D surveys to underground. No need to revise existing sensors implies also millions of saving and possibility to dual use sensors used for surface measurements.
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Void Detection and Consolidation Filling Verification by ERT, GPR and Seismic Refraction Methods
Authors G. Vargemezis, P. Tsourlos, I. Fikos, N. Diamanti, D. Angelis and E. AmanatidouSummaryThe present work deals with the application of applied geophysical methods to voids by two different approaches. The one refers to the detection of the voids and the second to monitor the consolidation of the ground. Three different methods are tested in both these two phases, resistivity, ground penetrating radar and seismic refraction. Initial geophysical survey was based mainly on resistivity and GPR methods, which allowed the detection of possible voids who were drilled after the suggestion of the geophysical results. All voids verified by the drilling were filled by a mix of soil and cement. Just before the start of the filling procedure, ERT, GPR and seismic data have been produced and measurements repeated again after the end of it, in order to verify the complete filling of the voids.
The response of the geophysical data was very clear since all geophysical features indicating the existence of the voids, vanished and showed the success of the consolidation process
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Non-Invasive Characterisation of Cement-Based Materials by Spectral Induced Polarization
Authors J. Holzhauer, P. Dick and A. RevilSummaryIn the context of radioactive waste management, concrete is used at various levels of the radioactive waste repositories. For safety purposes, it is of fundamental importance to characterise the mechanical integrity and chemical alteration of cementitious materials. While various sensors have been developed to provide punctual information on concrete infrastructures, indirect non-intrusive methods are still scarce. Spectral induced polarization (SIP) has been considered to fill this gap, based on its sensitivity to both fluid content and specific surface area, the latter being in connection with chemical alterations and pore-fluid interface evolution.
The frequency-dependent polarization of different CEMI and CEMV cement types was investigated for various formulations determined by water/cement ratio and possible aggregate addition. SIP measurements provide complex conductivity values, both at early-age and mature stages.
First results show an increase of both real and complex conductivity components with increasing water/cement ratios, and a decrease but proportional electrical response of mortars (obtained by addition of a resistive sand aggregate) with regard to their corresponding hardened cement pastes. The proportionality coefficient seems independent from the water/cement ratio. The eventual aim is to achieve homogenous quantifiable damaging of the cement-based samples, as to test the observability of its impact on polarization measurements.
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Comparison of Reflection Seismic Data with Seismic Tomography in an Underground Environment
By T. DickmannSummarySite investigations ahead of the tunnel face by means of geophysical methods are increasingly becoming an essential part of the risk management process for the last 20 years. Seismic methods have established as the frontrunner offering a wide range of data acquisition techniques, data processing types and result visualization tools. Continuous seismic measurements look for optimising both data acquisition process as part of the operative work flow while tunnelling and the rapidness in providing reliable geological predictions for the next tens of meters ahead of the face. To cope with the scenario that no explosives are available, the use of an alternative impact source together with continuous measurements is foreseen. By comparing TSP reflection seismic results of a sporadic measurement with results of high resolution seismic tomography in a test gallery, important insights about the penetration depth and resolution of the TSP results was possible. In the shown example, reliable results were obtained until about 50 meters away from the seismic layout.
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Example of a Survey in Transition Area for Construction Purposes
Authors A. Turchkov, A. Oshkin, V. Ignatev, A. Konkov, E. Samsonov and I. DmitrievSummaryThis paper is aimed to highlight both equipment and measurement techniques that may be effectively used for studying such complex sites (in comparision with standard near-surface seismic) as transition areas. The proposed solution allowed to obtain final sections that are suitable for further interpretation and linking the marine and land data for construction purposes.
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Keynote - Use of Geophysics to Provide Input Properties to Geotechnical Calculations
By M. LongSummaryCivil and geotechnical engineers have used geophysical techniques for many decades. However more recently geophysics is being used to provide input parameters for civil / geotechnical engineering design and numerical modelling. The examples given include use of GPR to give very detailed profiles at peat sites and Vs to give very good first order estimates of soil strength and stiffness properties.
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Evaluation of Dispersion Diagrams Distances Based on Usual Histogram Analysis for the Surface Wave Difference Inversion
Authors A. Wang, D. Leparoux, O. Abraham and M. Le FeuvreSummaryIn some recent geophysical monitoring studies, researchers have proposed a method of difference inversion, which means taking the difference between data into inversion process. It overcomes the crucial problem of the initial model for local optimization and reduce the environmental or system error in the results. Until now, there has not been an application of this method in the global inversion of Seismic Surface Waves. However using directly the difference between the dispersion curves as the data to be inverted can be not robust. Here, we propose to calculate differences between dispersion diagrams, which contains a part of the measurement uncertainty. Based on histograms distances definitions, several diagram distance calculations are used and tested numerically and experimentally in order to study the impact of the distance definition on the misfit assessment in case of a small variation about 10% in a deep part of a 2-layer medium. Results show the feasibility of this method. even if the accuracy of the the inversion result of the preliminary part remains a key issue on the assessment of medium’s variation.
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Exploring and Modelling the Qanat Gallery Path Using Electrical Resistivity Tomography Data
Authors A. Najafabadipour and G. KamaliSummaryApplying different optimal methods like Semi-Newton method results in modelling as well as interpreting the acquired data. Tikhonov regulation parameter was used for minimizing the objective function. The present study was conducted to explore and model the path and depth of the qanat gallery, bedrock and water table with sufficient resistivity compared to its surrounding area using electrical tomography data. According to the deep targets, the acquisition of data was made by using Schulmberger array with 3 profiles and 12 soundings. For inverting the data and constructing a 3D model of them, IPI2WIN software and VOXLER software were used respectively. The results revealed that as the qanat was water bearing the direction of its gallery path was from the southwest to the northeast at an approximate depth of 10 meters and with the electrical resistivity of about 100-ohm meter. According to the geological information, the bedrock was dolomitic having the electrical resistivity of almost 550-ohm meter compared to the surrounding area. The water table was about 16 meters being lower than the qanat gallery. The size of grains belonging to quaternary sediments were estimated as well.
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Performance Assessment of Novel Offshore Cable Detectors Based on Synthetic Data
By T. StolzSummarySubmarine power cables are an important infrastructure in modern times to connect, for example, separate energy power grids or offshore windfarm with the mainland. The position of these buried cables is often known only roughly after installation due to several reasons. Therefore, a cable tracking system is used which can detect the cable’s position. In this thesis, a novel system is presented which is based on inverting the magnetic field measured which is created by an active signal in the cable. An array of five three-axis fluxgate magnetometers measure the magnetic flux. Two different algorithms for detection are introduced. The first method relies on a simple model of the cable and a non-linear system of equation to estimate the location by inverting the total magnetic field measured by each sensor. The second approach uses the three-axis measurements to get the direction where the cable is from each sensor. The distance to the sensor array can be than estimated by using at least three different direction measurements. Both approaches are evaluated on synthetic data obtained by modelling the magnetic response of a cable in a marine environment.
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Advanced Signal Processing Method for Detection Surface Inhomogeneities from a Reflected Signal
Authors N. Antonyuk, M. Klein Wolterink, S. Kataeva and S. KataevSummaryAbstract – The successful realisation of high performance radars requires sophisticated methods and algorithms capable of obtaining information about investigated objects.
This paper illustrates a new method to determine surface inhomogeneities and/or their shapes for centimetre, millimetre, and sub – millimetre waves based on a method for revealing structures (MRS) which is a powerful tool to analyse data by means of finding of spatial points in which signals have the greatest contrast concerning other background points.
Typical examples of such inhomogeneous (textured) areas are near-surface buried objects, snow-covered ground, water waves and many others.
The new suggested method was named as “BinREL” and can be considered a generic approach for advanced signal processing since it is not tied to the physical nature or a concrete form of probing signal.
The merits of the method has been evaluated by processing datasets obtained from Staal Technologies prototypes based on 60 GHz frequency modulated continuous wave (FMCW) radar application specific integrated circuit (ASIC): RIC60A. The inkjet - printed images were taken as an investigation example.
Index terms – signal processing algorithms, microwave imaging, FMCW, ASIC, radar measurements, radar applications.
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Beyond Locating - Resolving Unique Underground Utilities with a Handheld-Sized Stepped-Frequency Continuous-Wave (SFCW) GPR
Authors M. Kaufmann and I. TsalicoglouSummaryPulsed GPR has been the main GPR technology for more than 30 years. However, stepped-frequency continuous-wave (SFCW) GPR technology presents two documented advantages compared to pulsed GPR: a bandwidth wider than the typical definition of “UWB”, and an approx. up to 20 dB higher signal-to-noise ratio. This results in larger penetration depths and improved resolution without salt-and-pepper noise.
In late 2017, SFCW technology became commercially available for concrete, where a system with frequency range 0.2–4.0 GHz demonstrably delivers both better resolution and depth penetration without post-processing filters. Since 2018, the SFCW GPR instrument is increasingly used for locating shallowly-buried utilities, an application so far addressed with pulsed-GPR devices.
We collected SFCW GPR data in soil to investigate the reason behind this trend, revealing that the technology’s benefits extend beyond concrete.
The SFCW GPR system can not only detect closely-spaced utilities but also resolve them uniquely within a bundle as countable hyperbolas, within typical depths, even though it was not developed with this application in mind.
Thus, with SFCW GPR subsurface investigators receive information beyond a “dig / no-dig” decision and can deliver insights that improve BIM and increase clarity for all stakeholders of infrastructure planning, monitoring and maintenance operations.
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Ground Penetrating Radar for Site Investigations and Utility Locating – Case Studies from Leipzig and Dresden
Authors F. Koellner and A. SchuckSummaryEspecially in urban areas, where the survey areas are often covered by concrete or asphalt, ground penetrating radar (GPR) is an ideal, sometimes the only, geophysical method for site investigations and for locating buried utilities. In the two case studies presented, construction works for traffic infrastructure are planned at busy traffic intersections in the inner-cities of Leipzig and Dresden by the respective municipal transportation companies and it was required to explore the shallow soil stratigraphy, to locate old foundation structures as well as to verify existing documentation of pipe and cable networks. These objectives could be met by GPR surveys in a very efficient way. The structure of a completely covered historic bridge was imaged, old foundations of a theater destroyed in WW II and a former pedestrian bridge were identified, the documentation of pipes and cables was refined and an undocumented cable was found. By means of a D-GPS surveying, which is synchronized to the GPR system, the results of the GPR investigations are immediately available with a highly precise spatial reference and can easily be incorporated into a building information model (BIM).
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Detecting the Position of Impermeable Membranes Buried in the Subsurface
Authors P. Kruiver, M. Karaoulis, B. Beuving, M. De Kleine and V. HopmanSummaryPVC membranes are used as groundwater barriers in infrastructure works in situations with high groundwater levels. When reconstruction works are necessary, the position of the membrane in the subsurface needs to be known. Deltares developed a method based on Electrical Resistivity Tomography (ERT) using the high electrical resistivity of the PVC membrane. Modelling showed that the PVC membrane has a profound effect on the electrical field lines. Classical ERT employed from the surface does not have sufficient spatial resolution to locate the membrane. Electrodes need to be closely spaced and within ca. 1.5 m from the membrane. To this end, a prototype tool was developed that can be pushed in the ground and measure while approaching the membrane. This prototype was tested in the laboratory. Measurements at different distances from the membrane showed that the tool can detect the distortion of field lines. Inversion was used to pinpoint the position of the membrane within 10 cm. The next step is to develop a tool that can be used in the field.
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The Impact of Spatial Sampling and Polarisation in GPR Survey for Utility Mapping
Authors F. Lombardi and M. LualdiSummaryThe presented analysis has quantitatively evaluated the performance of different GPR survey strategy for the detection and mapping of buried utilities. Results have shown that just the acquisition of a set of sparse 2D profiles is not a reliable strategy, as detection performance drops in presence of complex subsurface geometries, for which the profile spacing might be too wide to properly reconstruct the situation. A step ahead is represented by a 3D survey, in which the increased acquisition effort is balanced by the improvements achieved in terms of reconstruction quality. Targets can be tracked out of the 2D domain, feature that is highly relevant in areas with multiple intersecting objects. However, depolarisation phenomena, critical factor for linear and elongated targets, can be efficiently neutralised by the acquisition and combination of mutually orthogonal GPR volume.
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Keynote - Geophysical Practice of UXO Detection
More LessSummaryWorld War II UXO detection is a present day subject due to the large amounts of ammunition that is still buried in the subsurface. These may pose a threat during digging activities at larger depths. Removal is a four phase process, including historical research and geophysical detection onshore and offshore. A range of geophysical techniques, including their (dis)advantages, is described. The methods selected are based on historical information, soil type, potential disturbing objects and efficiency.
Geophysical UXO detection, geotechnics and infrastructure planning are interrelated. UXO detection activities can be reduced by geotechnical information. Infrastructure planning delays can be reduced by on time initiation of UXO detection and removal and careful planning. Planning takes into account in detail the infrastructural activities that will be carried out, its phasing and possibilities for intermediate reporting of geophysical research outcomes.
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Keynote - Identifying the Research Needs for Developing a Digital Buried Infrastructure Management Practice
More LessSummaryWestern cities manage their buried utilities through a large number of distinctive owners. This current fragmentation of the utility sector, and the poor registration of utility locations in the past has created an underground puzzle containing data pieces with different formats, accuracies, and completeness. We argue that virtual technologies address this problem but require that basic modelling conditions be fulfilled first. To structure this discussion, we use literature on Building Information Modelling (BIM) technologies in construction. BIM supports construction management tasks through the use of object-based parametric design models. This enables 3D and 4D design reviews as well as multi-stakeholder scheduling and planning. Furthermore, BIM integration with geospatial data enables the on-site use of construction data for facility management. Based on the experiences from our lab, we explain that the utility sector should train engineers in 3D utility mapping, and develop 3D/4D underground data models for design, scheduling, and maintenance. Such 3D models consequently integrate with other geospatial data to support risk analysis, construction site decision making, and on-site Virtual Reality applications. Our lab currently works on these needs together with industry. It seeks collaboration with other partners that also contribute to BIM for buried infrastructure.
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BIM - the Key for Implementation of Geophysics in Infrastructure Planning
Authors M. Svensson and O. FribergSummaryTo make more use of geophysics in general and more continuously during a whole infrastructure project geophysical data and models must be more compatible with other geo related data and other design disciplines and CAD software. The way to reach this is standardization of data formats, data exchange formats, objectification and implementation of a classification system for these objects. This would also enable full BIM compatibility and make it possible to keep track on data and models in an LCC perspective. A few suggestions on how to achieve this is presented.
In this paper a case study where the GeoBIM concept is used in a large infrastructure project for efficient communication and handling of geophysical data and models is presented.
CoClass is suggested as the classification system being used for true objectification of all data and models - points, lines, surfaces, volumes - adding meta data and classifying the objects so they can be used in a true BIM manner, also in a LCC perspective. When CoClass is implemented in all systems in the industry the workflow will be independent of what tool or software one is using, no matter who is the stakeholder.
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The Use of Geophysics in Large Swedish Infrastructure Projects
More LessSummaryIn Sweden the use of geophysical investigation methods as complement to geotechnical investigations in larger infrastructure projects have increased during the last 10 years. One of the main reason’s is probably the increasing use of planning tools in 3D, which increases the need for better data coverage. However, geophysics is still not counted as a standard method in the toolbox for ground investigations and the amount of geophysical investigations carried out in Swedish infrastructure projects differ a lot, due to several reasons. This abstract will discuss how and why geophysical investigations become or not become a part of larger infrastructural projects in Sweden and also discuss what should be done in the future to promote the use of geophysical investigation techniques. The main points of actions concerns purpose and expectations, awareness, uncertainty, standards and tools.
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Keynote - Multi Source for Digital Underground Constructions
By P. DohmenSummaryUnderground constructions and tunnelling are characterised by a dynamic advancement of tunnel boring technologies, increasing TBM (tunnel boring machines) diameters and a broadening range of applicability driven by the progress of digitalisation. This development in association with the inherent heterogeneity of the underground and the uncertainty of ground parameters poses new challenges to reliable prognoses models. Digital models are a vital element for the limitation of risks, particularly if difficult conditions concerning geology or sensitive urban environments must be considered. To cooperate in teams worldwide and coordinate projects we start to combine different sources for a more holistic view to describe asset and environment.
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