scholarly journals Inferring transport characteristics in a fractured rock aquifer by combining single-hole ground-penetrating radar reflection monitoring and tracer test data

2012 ◽  
Vol 48 (11) ◽  
Author(s):  
Caroline Dorn ◽  
Niklas Linde ◽  
Tanguy Le Borgne ◽  
Olivier Bour ◽  
Maria Klepikova
Keyword(s):  
Test Data ◽  
Ground Penetrating Radar ◽  
Fractured Rock ◽  
Tracer Test ◽  
Single Hole ◽  
Radar Reflection ◽  
Fractured Rock Aquifer ◽  
Ground Penetrating

scholarly journals Hydrogeophysical characterization of transport processes in fractured rock by combining push-pull and single-hole ground penetrating radar experiments

2016 ◽  
Vol 52 (2) ◽  
pp. 938-953 ◽  
Author(s):  
Alexis Shakas ◽  
Niklas Linde ◽  
Ludovic Baron ◽  
Olivier Bochet ◽  
Olivier Bour ◽  
...  
Keyword(s):  
Ground Penetrating Radar ◽  
Fractured Rock ◽  
Transport Processes ◽  
Single Hole ◽  
Ground Penetrating

Ground‐penetratinng radar reflection profiling of groundwater and bedrock in an area of discontinuous permafrost

Geophysics ◽  
1998 ◽  
Vol 63 (5) ◽  
pp. 1573-1584 ◽  
Author(s):  
Steven A. Arcone ◽  
Daniel E. Lawson ◽  
Allan J. Delaney ◽  
Jeffrey C. Strasser ◽  
Jodie D. Strasser
Keyword(s):  
Ground Penetrating Radar ◽  
Relative Dielectric Permittivity ◽  
Well Log ◽  
Surface Conditions ◽  
Continuous Contact ◽  
Interior Alaska ◽  
Discontinuous Permafrost ◽  
Radar Reflection ◽  
Ground Penetrating ◽  
Scattering Losses

We have used ground‐penetrating radar to profile the depth of permafrost, to groundwater beneath permafrost, and to bedrock within permafrost in alluvial sediments of interior Alaska. We used well log data to aid the interpretations and to calculate dielectric permittivities for frozen and unfrozen materials. Interfaces between unfrozen and frozen sediments above permafrost were best resolved with wavelet bandwidths centered at and above 100 MHz. The resolution also required consideration of antenna configuration, season, and surface conditions. Depths to subpermafrost groundwater were profiled where it was in continuous contact with the bottom of the permafrost, except near transitions to unfrozen zones, where the contact appeared to dip steeply. The complexity of the responses to intrapermafrost bedrock, detected at a maximum depth of 47 m, appears to distinguish these events from those of subpermafrost saturated sediments. The relative dielectric permittivity ranged between 4.4 and 8.3 for the permafrost, and between 12 and 45 for partially to fully saturated, unfrozen silts and sands. Scattering losses are evident from intrapermafrost diffractions and from the improved penetration achieved by lowering the midband radar frequency from 100 to 50 MHz.

Time-lapse ground penetrating radar difference reflection imaging of saline tracer flow in fractured rock

Geophysics ◽  
2020 ◽  
Vol 85 (3) ◽  
pp. H25-H37 ◽  
Author(s):  
Peter-Lasse Giertzuch ◽  
Joseph Doetsch ◽  
Mohammadreza Jalali ◽  
Alexis Shakas ◽  
Cédric Schmelzbach ◽  
...  
Keyword(s):  
Ground Penetrating Radar ◽  
Fractured Rock ◽  
Sampling Rate ◽  
Time Lapse ◽  
Transport Processes ◽  
Local Data ◽  
Tracer Injection ◽  
Flow Through ◽  
Reflection Imaging ◽  
Ground Penetrating

The characterization of flow and transport processes in fractured rock is challenging because they cannot be observed directly and hydrologic tests can only provide sparse and local data. Time-lapse ground penetrating radar (GPR) can be a valuable tool to monitor such processes in the subsurface, but it requires highly reproducible data. As part of a tracer injection experiment at the Grimsel Test Site (GTS) in Switzerland, borehole reflection GPR data were acquired in a time-lapse survey to monitor saline tracer flow through a fracture network in crystalline rock. Because the reflections from the tracer in the sub-mm fractures appear extremely weak, a differencing approach has been necessary to identify the tracer signal. Furthermore, several processing steps and corrections had to be applied to meet the reproducibility requirements. These steps include (1) single-trace preprocessing, (2) temporal trace alignment, (3) correction of sampling rate fluctuations, (4) spatial trace alignment, (5) spike removal, and (6) postprocessing procedures applied to the difference images. This allowed successful tracer propagation monitoring with a clear signal that revealed two separate tracer flow paths. The GPR results are confirmed by conductivity meters that were placed in boreholes in the GTS. If sufficient data processing is applied, GPR is shown to be capable of resolving tracer flow through sub-mm aperture fractures by difference reflection imaging even in challenging surroundings where many reflectors are present.

scholarly journals Ground-penetrating-radar response to fracture-fluid salinity: Why lower frequencies are favorable for resolving salinity changes

Geophysics ◽  
2008 ◽  
Vol 73 (5) ◽  
pp. J25-J30 ◽  
Author(s):  
Georgios P. Tsoflias ◽  
Matthew W. Becker
Keyword(s):  
Electrical Conductivity ◽  
Ground Penetrating Radar ◽  
Field Experiments ◽  
Fractured Rock ◽  
Low Frequency ◽  
Signal Amplitude ◽  
Time Lapse ◽  
Fracture Aperture ◽  
Fracture Fluid ◽  
Ground Penetrating

Time-lapse ground-penetrating-radar (GPR) surveys exploit signal-amplitude changes to monitor saline tracers in fractures and to identify groundwater flow paths. However, the relationships between GPR signal amplitude, phase, and frequency with fracture aperture and fluid electrical conductivity are not well understood. We used analytical modeling, numerical simulations, and field experiments of multifrequency GPR to investigate these relationships for a millimeter-scale-aperture fracture saturated with water of varying salinity. We found that the response of lower-frequency radar signals detects changes in fluid salinity better than the response of higher-frequency signals. Increasing fluid electrical conductivity decreases low-frequency GPR signal wavelength, which improves its thin-layer resolution capability. We concluded that lower signal frequencies, such as [Formula: see text], and saline tracers of up to [Formula: see text] conductivity are preferable when using GPR to monitor flow in fractured rock. Furthermore, we found that GPR amplitude and phase responses are detectable in the field and predictable by EM theory and modeling; therefore, they can be related to fracture aperture and fluid salinity for hydrologic investigations of fractured-rock flow and transport properties.

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