Journal of Environmental & Engineering Geophysics (JEEG)

Current Issue: Dec., 2018 Vol. 23.4

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A Forward by the Editor
Dale Rucker

As editor of a peer reviewed scientific journal, there are important aspects of publication of which I must be cognizant. On my ResearchGate blog, I have written about the impact factor and how it has been increasing over the past couple of years. The impact factor is a measure of how important the journal is to the scientific community. Submissions are another aspect that we continually try to improve. Submissions give us content to share and we on the editorial board have been doing outreach to help increase the number of submissions.  I believe this year will top the last. Readership, revenue, and costs are other items that we need to balance to ensure the long term viability of the journal. 

This last piece, cost, is driving a new decision for the journal to move away from print and into an online-only option for access. Over the past few years, the number of printed copies of JEEG has dropped as members of EEGS opt for lower costs for their membership. This has helped in making the decision to move exclusively online, as most readers get access to JEEG through internet clearinghouses (SEG, Geoscience world, etc.).  The online-only access will start with the March 2019 issue. Nothing else will change – you can expect the same great quality and broad coverage of topics to read and cite for your research.

This last print issue of JEEG is a special issue representing an international ground penetrating radar conference: the 9th International Workshop on Advanced Ground Penetrating Radar (IWAGPR2017).  Coincidentally, I started my geophysical career with GPR, so I find this issue bitter sweet. Over the past couple of years, we have published some other excellent
GPR science including bridge deck mapping (Diamanti et al., 2017), root mapping (Simms et al., 2017), an investigation into cable effects (Babcock et al., 2016), soil mapping (Allred et al., 2016; Freeland et al., 2017; Zaremba et al., 2016), and a new borehole system (Ma et al., 2016). And you can be guaranteed that future GPR papers published in JEEG will push the boundary of the tool to exploit ever finer details of the subsurface. I, personally, look forward to reading them.

Influence of Concrete Carbonation on Electromagnetic Permittivity Measured by GPR and Capacitive Techniques
1*Xavier Dérobert, 1Géraldine Villain and 2Jean-Paul Balayssac1IFSTTAR, CS5004, F-44344 Bouguenais cedex, France; 2LMDC, INSA/UPS Génie Civil, F-31077 Toulouse cedex 04, France
*Corresponding Author Email: [email protected]

This paper addresses the effect of concrete carbonation on the propagation and dispersion of electromagnetic (EM) waves and the capability of two EM, non-destructive techniques to detect this pathology. A capacitive technique operating at low frequency (around 33 MHz) and a ground penetrating radar (GPR) with a 1.5 GHz antenna were tested for the monitoring of reinforced concrete structures. To better understand the phenomena involved in concrete carbonation, the results of two complementary experimental campaigns were analyzed for saturated concretes. First, the dispersion curves of complex permittivity were measured for both carbonated and non-carbonated samples by a cylindrical coaxial EM cell. Due to carbonation, the permittivity decreased and the level of dispersion reduced slightly. Second, using GPR (coupled at approximately 900 MHz) and capacitive measurements conducted on controlled slabs, it was confirmed that the real part of the relative permittivity decreased within a range of 2 at 33 MHz and a range of 1 to 900 MHz, while the radar signal amplitude increased.

GPR Measurements for Spatial Investigations at the Asse Salt Structure
Volker Gundelach11Federal Institute for Geosciences and Natural Resources (BGR) Hannover, Germany
Email: [email protected]

The potash mine in the Asse salt structure, now used as repository for nuclear waste, is in some parts going to be refilled for mechanical stability reasons. As a part of that work, old blind shafts were prepared and offer the option for ground penetrating radar (GPR) measurements on vertical profiles in the mine. Horizontal profiles can be carried out in accessible drifts at the margin of the mine. The salt structure has mainly been explored from the surface by seismic measurements and boreholes. Due to the accuracy of these investigations and the openings and drifts inside the mine, the geological composition of the salt structure is known. East of the mine, the geological model is based on little information. Therefore, boreholes were drilled in that region and direction sensitive borehole tools provide additional structural knowledge. Vertical, horizontal and radial profiles in the mine have allowed imaging the complex geological structural information by mapping distance and direction of reflecting objects. With these results, a three dimensional geological model of the salt structures can now be optimized. This project is conceived and controlled by the operator of the mine the German Federal company BGE (Bundesgesellschaft für Endlagerung). BGR is commissioned amongst others for GPR measurements. 

Automated Data Extraction from Synthetic and Real Radargrams of Complex Structures
Željko Bugarinović1*, Simone Meschino2, Milan Vrtunski1, Lara Pajewski3, Aleksandar Ristić1, Xavier Derobert4 and Miro Govedarica11Department of computing and control engineering, Faculty of technical sciences, University of Novi Sad, Trg Dositeja Obradovića 6, 21000 Novi Sad, Serbia; 2Airbus DS GmbH, Claude-Dornier-Str. 88090 Immenstaad, Germany; 3Department of Information Engineering, Electronics and Telecommunications, Sapienza University of Rome, Via Eudossiana 18, 00184 Rome, Italy; 4IFSTTAR, GERS Department, LUNAM University, Bouguenais, France
*Corresponding author email: [email protected]

This paper presents a comparative study of two algorithms for detecting and analyzing the characteristic shapes of reflection obtained as a result of Ground-Penetrating Radar (GPR) scanning technology. The first algorithm is a sub-array processing method that uses direction-of-arrival algorithms and the matched filter technique; this approach is implemented in SPOT-GPR (release 1.0), a new freeware tool for the detection and localization of targets in radargrams. The second algorithm, APEX, is based on machine learning and pattern recognition techniques and it allows finding the coordinates of apexes and further characteristic points of hyperbolas in radargrams. Both software solutions are implemented in MATLAB environment. As a first step, we compare the accuracy of our algorithms when applied to synthetic data, calculated by using the open-source finite-difference time-domain simulator gprMax; the scenarios are two concrete cells hosting different metallic and dielectric targets. Then, we compare the accuracy of our algorithms when applied to experimental data, recorded over district heating pipes in a trench, with known geometry and depth of the pipes. For the latter scenario, we have also generated a gprMax radargram, matching the geometry and scanning settings of the real one; both algorithms are tested on this synthetic radargram, as well. Overall, both algorithms perform well and rather uniformly in localizing the targets. The accuracy of the algorithms is at centimeter level, which is sufficient in most applications.

Assessing Ground Penetrating Radar’s Ability to Image Subsurface Characteristics of Icy Debris Fans in Alaska and New Zealand
Robert W. Jacob1*, Jeff M. Trop 1, and R. Craig Kochel 11 Department of Geology and Environmental Geosciences, Bucknell University, Lewisburg, PA
*Corresponding author email: [email protected]

Icy debris fans have recently been described as fan shaped depositional landforms associated with (or formed during) deglaciation, however, the subsurface characteristics remain essentially undocumented. We used ground penetrating radar (GPR) to non-invasively investigate the subsurface characteristics of icy debris fans (IDFs) at McCarthy Glacier, Alaska, USA and at La Perouse Glacier, South Island of New Zealand. IDFs are largely unexplored paraglacial landforms in deglaciating alpine regions at the mouths of bedrock catchments between valley glaciers and icecaps. IDFs receive deposits of mainly ice and minor lithic material through different mass-flow processes, chiefly ice avalanche and to a lesser extent debris flow, slushflow, and rockfall. We report here on the GPR signal velocity observed from 15 different wide-angle reflection/refraction (WARR) soundings on the IDFs and on the McCarthy Glacier; the effect of GPR antenna orientation relative to subsurface reflections; the effect of spreading direction of the WARR soundings relative to topographic contour; observed differences between transverse electric (TE) and transverse magnetic (TM) antenna polarization; and a GPR profile extending from the McCarthy Glacier onto an IDF. Evaluation of the WARR soundings indicates that the IDF deposits have a GPR signal velocity that is similar to the underlying glacier, and that the antenna polarization and orientation did not prevent identification of GPR reflections. The GPR profile on the McCarthy Glacier indicates that the shallowest material is layered, decreases in thickness down fan, and has evidence of brittle failure planes (crevasses). The GPR profile and WARR soundings indicate that the thickness of the McCarthy Glacier is 82 m in the approximate middle of the cirque and that the IDF deposits transition with depth into flowing glacial ice.

The WARR Machine: System Design, Implementation and Data
Nectaria Diamanti1, 2, *, E. Judith Elliott1, Steven R. Jackson1, A. Peter Annan11Sensors & Software Inc., 1040 Stacey Court, Mississauga, L4W 2X8, ON, Canada; 2 Now at the Department of Geophysics, Aristotle University of Thessaloniki, 54124, Greece
*Corresponding Author Email: [email protected]

In this paper, we describe a GPR system called the WARR (wide angle reflection and refraction) machine, outline the design and discuss the implementation challenges. WARR and the closely related CMP (common-mid-point) GPR soundings have been standard survey methods to measure velocity since GPR first existed. Earliest efforts demonstrated the variation in ice sheet velocity versus depth. Although GPR multi-offset soundings are valuable survey methods, they have seen little adoption since many systems are not bistatic. In addition, surveys most often use a single transmitter with a single receiver deployed sequentially at varying antenna separations, making data acquisition slow.

Modern instrumentation with recent advances in GPR timing and control technology has enabled deployment of systems with multiple concurrent sampling receivers. This development has resulted in the ability to continuously acquire multi-offset WARR data at the same rate as two dimensional (2D) common offset reflection surveys in the past. The concomitant issues of survey design plus organizing the WARR data storage, documentation and analysis present numerous challenges. The extraction of velocity information from the large volumes of GPR WARR/CMP data demands automated analysis techniques. We have explored the use of normal move out (NMO) stacking at creating enhanced zero offset section from multi-offset data. Furthermore, we investigated the use of semblance analysis at estimating move-out velocities in order to apply in the NMO stack. These traditional seismic processing steps have proven to be less effective with GPR. These conclusions point to the differences in data character between seismic and GPR. Results of in-field deployment are used to illustrate advances to date and point the way to further advancements.

An Innovative Use of TDR Probes: First Numerical Validations with a Coaxial Cable
Raffaele Persico1,2, Iman Farhat3, Lourdes Farrugia3, Sebastiano D’Amico4, Charles Sammut3
1: Institute for Archaeological and Monumental Heritage IBAM-CNR, Italy
2: International Telematic University Uninettuno, UTIU, Italy
3: Department of Physics, University of Malta, Msida, Malta 
4: Department of Geosciences, University of Malta, Msida, Malta

In this paper we propose a study regarding some possibilities that can be offered by a time domain reflectometry (TDR) probe in retrieving both dielectric and magnetic properties of materials. This technique can be of interest for several applications, among which the characterization of soil in some situations. In particular, here we propose an extension of the paper “Retrieving electric and magnetic properties of the soil in situ: New possibilities”, presented at the IWAGPR, held in Edinburgh in 2017, and as a new contribution we will validate a transmission line model with numerical data simulated by the CST code.

Measurement of Bulk Electrical Properties Using GPR with a Variable Reflector
J. David Redman1, A. Peter Annan1, Nectaria Diamanti1,2,* 1Sensors & Software Inc., 1040 Stacey Court, L4W 2X8, Mississauga, ON, Canada; 2 Now at the Department of Geophysics, Aristotle University of Thessaloniki, 54124, Greece
*Corresponding Author Email: [email protected]

Bulk electrical properties of media are important inherently for ground penetrating radar (GPR) applications and for providing a means to determine indirectly other physical properties such as moisture content. We have developed a reflector whose reflectivity can be controlled electronically. This variable reflector controlled by a GPR provides an effective method to measure bulk electrical properties of media. For sample measurements, the GPR is placed on one side of a sample and the variable reflector on the opposite side. GPR trace data are then acquired with the reflector in an on-state and in the off-state. By differencing these measurements, we improve the ability to detect the specific reflection event from the variable reflector. This process removes both the direct wave and clutter from the trace data, improving the quality of the refection event and our ability to accurately pick its arrival time and amplitude. We describe the variable reflector, a prototype instrument based on the reflector and numerical modeling performed to understand its response. We also show the results of testing applications to the measurement of wood chip moisture content and monitoring of the electrical properties of concrete during the curing process.

GPR Study of a Thrust-Fault in an Active Limestone Quarry (SW Slovenia)
1*Marjana Zajc, 2,3Andrej Gosar and 1Bogomir Celarc1Geological Survey of Slovenia, Dimičeva 14, 1000 Ljubljana, Slovenia; 2Faculty of Natural Sciences and Engineering, University of Ljubljana, Aškerčeva 12, 1000 Ljubljana, Slovenia; 3 Slovenian Environment Agency, Seismology and Geology Office, Vojkova 1b, 1000 Ljubljana, Slovenia
*Corresponding Author Email: [email protected]

After conducting a successful GPR pilot study in a tectonically complex area of the Karst Thrust Edge, a follow-up study was carried out. In the pilot study, the geometry and spatial extent of the Socerb thrust-fault, which separates limestone above from flysch below, were investigated using a 50 MHz antenna in the Črnotiče quarry. After one part of the quarry was deepened and widened, new flysch outcrops were exposed and GPR profiling was made possible in areas where the thrust contact could not be reached before. By comparing the first GPR results with the locations of new flysch outcrops, we found it reached the surface almost exactly where we had predicted. In order to gain new information about the location of the thrust contact, nine new profiles were recorded. In this newly deepened area, the thrust contact runs close to the surface, therefore a 250 MHz antenna was used in addition to the 50 MHz antenna in order to ensure an adequate level of resolution. This combination of antennas provided the depth penetration of 34 m as well as resolution high enough to obtain accurate information from the shallowest parts. GPR profiles were used to create a 3D model of the thrust-fault plane, providing information about the spatial position and lateral undulations of the thrust contact. The results provided new data about the geometry of the Socerb thrust-fault and correlated well with existing borehole data. The results also showed the importance of using appropriate antenna frequencies as other features capable of becoming hazardous during excavation (air-filled and sediment-filled karst caves) could otherwise be misinterpreted or overlooked. The follow-up research not only provides new data important for understanding the tectonic setting of the area, but also information needed for calculating exploitable material quantities and for planning safe excavation processes.

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