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Near Surface Geoscience 2015 - 21st European Meeting of Environmental and Engineering Geophysics
- Conference date: September 6-10, 2015
- Location: Turin, Italy
- Published: 06 September 2015
21 - 40 of 164 results
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Drones — New Technologies for Geophysics?
Authors A. D’Alessandro, F. Bucalo, M. Coltelli and R. MartoranaSummaryDrones, also referred as Unmanned Aircraft Systems (UAS), Unmanned Aerial Vehicles (UAV) or Remotely Piloted Aircraft (RPA), are aircraft without pilot on board. USA is today the leading country in the field of UAS but recently, seven European countries have pledged to launch joint programs for drones, with the aim of producing the next generation of UAS before 2020. According to some studies on the potential market of UAS in Europe, the geoscience sector is definitely one of the most promising. In this paper, we bring a short description and classification of drones, according to their sized and shaped, with particular attention to the advantages and drawbacks of each type in reference to the possible employment in geosciences applications. Currently the drones are used for geological and topographic mapping, coastal control, landslide inspections, etc., and are capable to integrate geophysical sensors like magnetic, electromagnetic, infrared, radar, natural gamma ray sensors and etc.
UAS technology have several advantage over conventional airborne geophysics like resolution, accurancy, cost, etc. We are witnessing the birth of a new branch of aviation, which could be profitably applied to geophysics measurements.
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The Use of Mathematical Models in the Control Environment of Underground Gas Storage
SummaryThe operation of underground gas storages may be accompanied by deterioration of the technical condition of wells. This is due primarily to the variables of temperature and pressure loads of the element in the wellbore during injection and extraction of gas, which most from the earth’s surface and to a depth of 500–700 m. Under the influence of these factors disrupted the adhesion of cement to casing and formation, occur the leakage of columns, gas leakage from the wellbore, the accumulation of gas behind the columns and headers, behind-the-casing flows from the storage reservoir into the overlying sediments. All this results in considerable industrial gas accumulations, the complication safe operation of UGS and disturbance of the ecological situation in the area. Therefore, the development of the technology search wells — sources of technogenesis, elimination of leaks and cross-flows of gas in them is an urgent task for underground gas storage. The work deals with the identification of cross-flows in the wells of underground gas storages. We consider mathematical models and algorithms for identifying cross-flows according to the thermometer wells. Examples of the interpretation and processing of data, previous studies of wells, underground gas storage.
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Fast Multi-channel Data Transfer System for Ultrasonic Borehole Tools and Others
By T. RadicSummaryReliable and high resolution information about the current state of radioactive waste repositories and their casing can only be gained on site with borehole tools. Ultrasonic sensors are such a tool, making it possible to characterise the surrounding ground (salt, clay, granite) by measuring the elapsed times of high frequency seismic signals. The arising data must be transmitted to an above ground or to a subterranean observation point. There, the data (mostly still analogue signals) are collected, plotted and quantitative evaluated. The quality of the transmitted analogue signal is, however, reduced through, amongst others, the excitation signal (which is usually transmitted through analogue means). This problem becomes more severe as the distance of transfer increases. We are currently developing a digital data transfer system, which will span a distance of up to 2 km. This system allows 7 analogue signals, with a bandwidth of 250 kHz each, to be transmitted within a single optical fibre at the same time. The same single fibre is used in the opposite direction to remote control gain settings and others. Further areas of use lie where rapidly changing analogue signals must be transmitted in real time over large distances.
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Comparison of Different Acquisition Patterns for 2D Tomographic Resistivity Surveys
Authors R. Martorana, P. Capizzi, A. D’Alessandro and D. LuzioSummaryA systematic comparison is presented between some 2D resistivity models and their images by the inversion of synthetic datasets relating to three different arrays, suitable for multichannel data acquisitions (dipole-dipole (DD), Wenner-Schlumberger (WS) and multiple gradient (MG)). The goal is to study how the measurement errors affects the resolution of the tomographic models and the ability to retrieve correct information on buried targets. We considered different data acquisition patterns, gradually increasing the complexity of the combinations of potential spacing and dipolar distance. To this end we increased the number of current dipoles to obtain approximately the same amount of measures, increasing the investigation time. Results from noise-free and noisy data are discussed and compared with those from field data. The results show that: the quality of the inversion models, for a fixed noise level, depends significantly on the data acquisition pattern; the information recovery and the resolution, being equal the number of measurements, is overall better for WS and worse for DD; the decrease of sensitivity with depth is lower for particular acquisition patterns that allow to better resolve deeper targets; the MG array can be preferred because it provides comparable results, using a smaller number of current electrodes.
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Site Investigation of Twin Tunnels by Joint Application of Seismic and Engineering Geophysical Soundings (CPTe)
Authors É.B. Bujdosó, E.H. Hegedűs, A.C.K. Kovács, I.T. Török, R.C. Csabafi and J.S. StickelSummaryThe near-surface geophysical data have become key components in the development of the engineering of major underground structures. Geological and Geophysical Institute of Hungary (GGI of Hungary) carried out a detailed geophysical survey along the twin tunnels of a new Metro line in Budapest, Hungary. Following the tunnel boring activity several sinkholes were detected at the surface along the path of the twin tunnels. GGI of Hungary carried out engineering geophysical soundings (CPTe) and non-invasive seismic technologies (3D seismic tomography) in order to mitigate the potential risk of any material damages in the future. The aim was to get to know the physical parameters of the soil layers. The joint application of the two methods was able to detect the known and the hidden potential sinkholes using state-of-the-art technology.
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MASW 2D Seismic Survey in Urban Areas - The Case of the Turin Metro 1 Line
Authors C. Alessio, R. Crova, E. Duò and M. NaldiSummaryThe present article discuss the results of seismic investigation conducted in Turin, Italy, to assess the geological and geotechnical modeling related to the planned extension of the underground Metro Line 1 from Collegno to Cascine Vica (about 4 km of length, from Collegno to Cascine Vica). The specific objectives were to map the thickness of the man-made ground lying upon alluvial soil made of gravel and sand and evaluate the stiffness property of the subsoil. To overcome the typical obstacles of the urban ambient (electromagnetic and vibrational noise, hard traffic management, high energy source required) we applied the shallow wave technique with a continuous profiling (MASW 2D) by means of a customized system of geophones array on a land streamer and a controlled source of energy mounted on a vehicle. The surveys were performed overnight in two sessions (two days), with a fast data acquisition for a total length 2000 m. The results of the survey, calibrated with boreholes positioned all along the survey line, has precisely mapped the contact between the shallow reworked ground and the alluvial deposits. Moreover, the survey results have highlighted many lenses of cemented gravel (conglomerate bodies) inside the alluvial deposits.
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Geophysics and Tunneling - The How and the Why - A Focus on the Why
Authors L. Sambuelli, P. Fargione, E. De Cillis and M. PatruccoSummaryTunnels should be constructed, maintained and used without neglecting the basic principia of Occupational Safety and Health (OS&H), environmental protection and economic efficiency: this involves a Prevention through Design approach both from the very first steps of the project, and during the tunneling operations. At the purpose, the identification and careful evaluation of a number of parameters are essential for a correct Risk Assessment and Management (RAM) during the various phases of the analysis. However, many of these parameters are “hidden into the mountain” and difficult to identify with the desired detail. This problem can affect the quality of the result, and cause accidents and work stoppages, with consequent dramatic economic losses.
In the Authors’ opinion, only a multidisciplinary approach can contribute to solve the problem. The already consolidated contribution of geophysics plays an important role, and represents an efficient means for a more efficient definition of the design parameters. Future developments in the research work in geophysics are advisable and precious for a more efficient predictive RAM, both at the preliminary phase, and during the tunneling operations, particularly if a fast response will become achievable.
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Geophysical Time-lapse Monitoring of Leachate Recirculation in a Bioreactor Landfill
Authors A. Arato, G. Cappato, F. Manfredi, M. Fischetti, E. Perissinotto and A. GodioSummaryThis work deals with the time-lapse geoelectrical monitoring of leachate re-circulation inside a municipal solid waste landfill. The studied landfill is exploited as an anaerobic bioreactor, and leachate is recirculated in order to maintain constant and high moisture content within the waste. The goal of leachate injection is to ensure optimal conditions for the anaerobic bacteria to rapidly degrade the organic fraction of the waste. The main objective of this study is to evaluate the electrical behavior of the wastes, for estimating the moisture content dynamics during time.
Electrical resistivity tomography (ERT) and self potential (SP) methods have been applied both on surface electrodes installed on the top of the landfill and along borehole which have been installed for cross-hole measurements.
Both the methods helped in locating the zones affected by the leachate flow, but ERT measurements suffered from anomalous long-term polarization phenomena. On the other hand, SP measurements were in good accordance with the injected leachate volumes, and they can be useful for helping numerical modeling of the leachate flow within the waste mass.
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Investigation Concrete Quality of Zigana and Torul Tunnels by Using GPR Method
Authors I. Saricicek and A. SerenSummaryThe GPR method which can display the shallow depth of the investigated surface with high reslution, is a widely- used method to investigate the concrete structure without any damage. In this study it is aim to investigate the leaking water risk areas and accordingly the evaluation of the content of the concrete structure of the Zigana Tunnel which located on the highway of Trabzon-Gümüshane and faracture-joint system, deterioration and stratigraphy of the Torul Tunnel walls. During examinations, GPR data were collected along totally 20 profiles at the entrance of the both sides of tunnels by using 500 MHz and 800 MHz shielded antennas. After applying essential data processing stages to the collected data, 2D and 3D images with ReflexW3DScan software were acquired. When analyzed amplitude-slice maps at various depths into the wall from these images; while has impaired in places of concrete structures in belonging to the Zigana Tunnel, those obtained from the Torul tunnel have been identified quite durable and high quality of concrete internal structure.
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Integrated Geophysical Investigations for Calcione Dam Safety Evaluation
Authors V. Giampaolo, L. Capozzoli, A. Caputi, C. Corradini, G. Zucco, T. Moramarco and E. RizzoSummaryAn integrated geophysical field investigations have been carried out at the Calcione earthen dam near Lucignano town (Arezzo, Italy), for the purpose of better understanding the hydrogeological conditions at the site. In winter 2002, the Calcione dam embankment has been affected by some landslides and a gabions drainage system was installed to mitigate the phenomena. Therefore, the purpose of the geophysical investigation has been to identify the presence of eventually seepage areas through the embankment materials and provide information about subsurface water circulation. These tasks have been accomplished through the use of self-potentials (SP), electrical resistivity tomography (ERT) and ground penetrating radar (GPR). The results obtained allowed to identify an area of interest in correspondence of the central area of the dam above the installed gabions drainage system. Moreover, future efforts will focus on an integrated hydro geophysical interpretation, where geophysical data will be directly incorporated into the dynamic estimation of hydrogeological parameters.
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S-wave Velocity Monitoring During an Artificial Rainfall Experiment Using Large Scale Rainfall Simulator
Authors C. Konishi, T. Ishizawa, T. Danjo and N. SakaiSummaryWe conduct the rainfall experiment using a large scale rainfall simulator and an artificial embankment consists of sand and silt in order to evaluate S-wave velocity monitoring for a prediction of a slope failure. The intensity of the rainfall is controlled to maintain 15 to 200 mm/hour for a certain time frame. S-wave velocity cross sections are acquired by MASW survey before, during, and after the controlled rainfall. The obtained cross sections show little change in the S-wave velocity and that is considered to reflect water filtration process in subsurface. The difference is not so significant, but it is confirmed by both waveforms and the dispersion curves calculated from common shot gathers at a fixed shot point. The dispersion curves are included various higher modes and that makes it difficult to evaluate the result; however, the complex higher mode would be useful to derive more information in the future. Compared to the resistivity monitoring, the S-wave velocity monitoring is not so sensitive to the water content; instead, it is relatively easy to be obtained by surface wave method. Therefore, it will be an effective monitoring tool to assess vulnerability of slopes and mitigate damage by natural disasters.
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Electrical Resistivity Tomography in Support of Geological Surveys of Landslides Involving Clay Slopes in Asti Reliefs
Authors D. Barbero, M.G. Forno, M. Naldi and A. TissoniSummaryWe report on the results of geological, geotechnical and geophysical surveys for the characterization of a landslide, occurred in the Asti Reliefs (NW Italy) during the first ten days of March 2011, just after an exceptional meteoric event. The investigated landslide is located in San Damiano d’Asti (15 km E of Asti) and involved a hilly side, gently sloping. The hazard situation in this area regards a landslide that involved the back of a building. This landslide was caused by excavations made in the time at the toe of the slope with the aim to extend the narrow flat spaces. The contribution given by Electrical Resistivity Tomography (ERT) was essential, in the first phase of the investigation, to recognize deep and localized water seepage, otherwise undetectable. The identification of saturated clays into the slope allowed us to design the correct re-profiling of the scarps and make digging operations in safely. The use of these methods of investigation has a significant economic savings in the choice of interventions for slope stabilization.
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Landslide Geophysical Imaging - Kapušany Landslide Case Study
Authors R. Putiska, I. Dostál, D. Kušnirák and M. BednárikSummaryGeophysical survey is very useful and popular tool used by engineering geologists to examine landslides. We present a case study from the Kapušany landslide, eastern Slovakia, where a broad spectrum of geophysical methods were applied on several profiles in order to compare the ability of the methods to detect as many landslide’s structural features as possible. The 2D Electrical Resistivity Tomography inverse model was capable to define the geological structure of the landslide and to define the shear zone, however the resolution of the inverse model does not allows us to identify cracks or other minor landslide’s features. These, however, were nicely recorded in the results of Dipole Electromagnetic Profiling and Self Potential method. In addition microgravity was employed to validate the results obtained from electrical methods and afterwards a final geological model, based on the integrated interpretation of all involved methods was constructed. This model will serve as a reference model for long term landslide monitoring using modern geophysical and engineering geological approaches.
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Detection of Landslide Plane by Using Refraction Seismic Tomography Method
More LessSummaryAn application of refraction tomographic method in order to identify a predicted landslide’s plane is presented. This method is applied to detect the existence and the geometry of possible landslide’s plane that is situated in a Seling Village, Kebumen City — Indonesia. This area experienced several episodes of landslide type of creeping several years ago. Although it has been observed that the displacement of the most upper part of surface is only several centimeters per years, but there is a tendency that bigger landslide could be occurred in the future.
The seismic data was acquired on the surface that has a total length of about 150 m. Twelve shots and 24 geophones are planted on the seismic line that is perpendicular to the predicted strike of landslide’s plane.
The result shows that the most upper part of surface has low P-wave velocity values. Higher P-wave velocity layer is situated below this layer. The plane between those layers is then interpreted as possible landslide’s plane. The result of this investigation is a P-wave velocity section, which correlates well with almost all available a priori data. Several resolution tests are conducted in order to increase the certainty degree of tomographic results.
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Geotechnical Risk Assessment at South Eastern Suburb of Cairo, Egypt Using Integrated Geophysical Techniques
Authors N.I. Medhat, M. Atya, E.A. Ragab, A. Ali and M. AbdelzaherSummaryThe reason for implementation of this research is the prevalent of incidences of structural damage around the area of investigation causing large number of casualties and loose of souls.
The location of the district is very close to the quarry blasting operations that can intensely produce stresses in the ground due to continuous artificial explosions and ultimately result in the instability of the area.
Geophysical reconnaissance surveys using seismic refraction, electrical resistivity and ground penetrating radar were carried out to measure near surface structure setting and follow up its activity upon time by delineating the major fault and other minor features such as cracks, fissures and water saturated zone.
Integration of the geophysical data shows that the main reason of fractures in the study area is the swelling of marly clay layer due to retention of the drainage water. Also, there is a near surface major fault cuts the southern part of the study area causing variation in thickness of the marly clay layer and consequently affect on the inhabitant buildings.
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Estimation of Alluvial Sediments Properties with a Multilevel Cluster Analyses of Spectral Induced Polarization Data
Authors S. Inzoli, M. Giudici and J.A. HuismanSummaryIn order to infer the sedimentological properties of saturated samples of alluvial deposits, a cluster analysis is applied on spectral induced polarization data (amplitude and phase resistivity spectra). The hierarchical tree of clusters is dissected and analyzed at different aggregation levels, comparing the electrical and sedimentological intra-cluster variability. A low number of clusters densely populated guarantees a perfect allocation into cluster on the base of a few electrical parameters but permits to obtain only a rough textural characterization of the sample, while increasing the number of clusters yields to reduce the variability intervals of the textural parameters and of the chemical properties of the saturation water within each cluster, thus reducing the uncertainty in their estimation. An excessively large number of clusters is ineffective since the uncertainly in the assignment of a sample to a specific cluster is too high. These results can be used as an indirect tool for sediments characterization and have been successfully tested on an independent sample. The cluster analysis allowed to use the whole spectral information to establish a link between geological and geophysical parameters, avoiding the use of one-to-one correlations, whose validity has not yet been confirmed for natural unconsolidated materials.
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Using Borehole NMR Data to Determine the Effective Porosity of Sediment for Groundwater Resource Estimation, Australia
Authors K.P. Tan, K.L. Lawrie, J. Abraham and R.S. BrodieSummaryEstimating groundwater storage volumes is important for assessing the potential capacity and recovery efficiencies of Managed Aquifer Recharge (MAR) strategies. However such volume estimates are vexed by poor characterisation of factors such as the effective porosity of the aquifer. These issues were faced by the Broken Hill Managed Aquifer Recharge (BHMAR) project which aimed to define key groundwater resources and aquifer storage options in the lower Darling River floodplain of western New South Wales, Australia. The aim of this study is to determine if the NMR free-water data depicts the effective porosity of the sediment and could be used in a workflow to estimate groundwater storage volumes in the target aquifer. 26 sonic drilled bores were logged using the Vista Clara Javelin system. An investigation ensued to validate these NMR results. This included examination of the NMR data processing parameters and optimal regularization factor, additional matric potential and gravimetric water experiments to determine the fractional water and total porosities of sediment. The laboratory experiments showed comparable results to the NMR free-water and total water for sand and muddy sand, but the NMR underestimated the total water in mud.
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Monitoring of Injection of Hydrogen Release Compounds in a Contaminated Site
Authors A. Arato, S. Fiore, B. Ruffino, A. Godio, M.C. Zanetti and C. RoatiSummaryWe present the set-up and results of a pilot-scale field test concerning the remediation of a site polluted by chlorinated solvents. The hydogeological setting is mainly compound by a first aquifer in silty and sandy material and a second fissured aquifer made of fractured grey marl and gypsum/sulphur formations. A preliminary characterisation of the area have pointed out the groundwater contamination by chlorinated solvents, at a depth of about 15–20 m b.g.l. Vinyl chloride was identified as the secondary pollutant, proving the occurrence of natural degradation phenomena. Hydrogen Release Compound (HRC-X, Regenesis) was selected to support the on-site biological activity. In a selected test site, we injected about 250 kg of reagent in three injection points at the depth of about 15–18 m.
The chemical and physical monitoring of the clean up activity was performed for about 6 month after the injection by groundwater sampling in the three observation boreholes (downstream with respect the injection points) and by time lapse cross-hole resistivity tomography.
The enhancement of natural attenuation phenomena is testified by the decrease of halogenated pollutants with higher number of chlorines, and by an enhancement of the amount of the reductive dechlorination secondary products.
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Detecting Contaminants in Aquifers through Modeling of Surface-downhole Geoelectrical Data
Authors M.V. Bongiovanni, V. Grünhut and A.M. OsellaSummaryMost of the world’s reservoirs are currently in the advanced primary or secondary recovery stage. Even though sinks wells used by oil companies are located much deeper than aquifers, they may eventually cause environmental damages contaminating the water with brine leakage, oil spill or other polluting agent. This is why it is extremely important to do vulnerability studies.
Since contaminants have different electrical conductivity than water, geoelectrical methods can be useful to detect and even monitor flow evolution of the contamination plume.
We want to analyze if it is possible to detect contaminations of an aquifer that lies above an oil reservoir, approximately at 300 m depth, with current injections on surface and voltages sensors in a well. In order to achieve this we have designed an electrical model of the reservoir including the contaminated aquifer with, either a conductive contamination such as saline brine or a resistive contamination such as oil spill, and numerically simulated the forward geoelectrical responses.
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High Amplitude SP Anomalies in Mountains of Electrokinetic Origin
Authors V.A. Shevnin, A.A. Ryjov and D.A. KvonSummaryIn different countries after 1967 were discovered local self potential anomalies above 1200 mV that didn’t related with redox processes in rocks. Such anomalies were found in mountains, they had inverse correlation with relief, and underground water had low mineralization and high electrical resistivity. Possible cause of these anomalies can be electrokinetic or streaming potentials due to water filtration. Calculation of electric field intensity on Helmholtz formula shows that these anomalies could appear at water resistivity above 100 Ohmm at filtration in loose sand-gravel- soil.
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