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  • 1
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    Investigation of an airborne resistivity survey conducted at very low frequency (1977)
    Hanover, NH : U. S. Cold Regions Res. and Eng. Laboratory
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    Call number: ZSP-201-77/20
    In: CRREL Report, 77-20
    Type of Medium: Series available for loan
    Pages: ix, 48 S. : graph. Darst.
    Series Statement: CRREL Report 77-20
    URL: https://apps.dtic.mil/docs/citations/ADA044684
    Note: CONTENTS Abstract Preface Summary Symbols Introduction Background Objectives Experimental procedures Principles of electromagnetic resistivity surveying Resistivity of earth materials Radiowave propagation within the earth-ionosphere waveguide Radiowave interaction with the earth Instrumentation Airborne Ground Methods Experimental procedures Test site Survey traverses Results Study no. 1 — standard survey Study no. 2 — topographic and resistive effects upon £ xq and £ z j Study no. 3 — general effects of altitude upon geologic resolution Study no. 4 — ground level study of phase and amplitude effects The standard survey reevaluated Conclusions and final remarks . Literature cited Appendix: Glossary of geologic terms used ILLUSTRATIONS Figure Electromagnetic field vectors of a radiowave propagating over the earth’s su rface Resistivity ranges of most earth materials Two radiowave propagation modes in the earth-ionosphere waveguide Coverage for well-known LF stations Simply layered flat earth model used for deriving the definitions of apparent resistivity and also used in modern data interpretation techniques Skin depth of radiowaves as a function of frequency for various values of resistivity
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  • 2
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    Interaction of a surface wave with a dielectric slab discontinuity (1978)
    Hanover, NH : U.S. Army Cold Regions Research and Engineering Laboratory
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    Call number: ZSP-201-78/8
    In: CRREL Report, 78-8
    Description / Table of Contents: The interaction of a 5.1-GHz transverse electric surface wave with a dielectric slab is experimentally investigated. The wave is initially supported by a dielectric substrate resting upon a metallic ground-plane. A slab, made of the same dielectric material as the substrate and variable in height, is then placed upon the waveguide. The results for a small slab sitting on the substrate showed that the discontinuity was a very inefficient launcher of reflected surface waves. Investigations of these reflections with a trough waveguide showed that, for values of slab height comparable to the exponential decay height of the surface wave, the reflections remain very small. However, as the slab height is increased beyond the decay height, the reflected amplitude approaches the theoretical value for a plane wave reflected from the interface between air and the same dielectric. The results are applicable to surface wave methods of microwave deicing of wings and helicopter rotors.
    Type of Medium: Series available for loan
    Pages: v, 16 Seiten , Illustrationen
    Series Statement: CRREL Report 78-8
    URL: https://hdl.handle.net/11681/9408
    Language: English
    Note: CONTENTS Abstract Preface Summary Introduction Background Objective and procedure Theory of plane surface waves Waveguide design and characteristics Physical apparatus Frequency characteristics Spatial distribution of Ey above the guide Guide wave length Surface wave interaction with a slab discontinuity Experiments with a trough Discussion and conclusions Literature cited
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  • 3
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    Radar profiling of buried reflectors and the groundwater table (1983)
    Hanover, NH : U.S. Army Cold Regions Research and Engineering Laboratory
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    Call number: ZSP-201-83/11
    In: CRREL Report, 83-11
    Description / Table of Contents: Investigations of ground radar performance over thawed and seasonally frozen silts, and sands and gravels containing artificial and natural reflectors were carried out in Alaska. The radar emitted 5-10 ns pulses, the center frequency of which was approximately 150 MHz. The artificial reflectors were metal sheets and discs and the natural reflectors were the groundwater table and interfaces between frozen and thawed material. The water table was profiled at three sites where the subsurface material was coarse-grained alluvium. Dielectric constants of 16 to 18 were measured for the thawed silts, 6 to 7 for the frozen silts and 3 to 9 for the sands and gravels. Signal penetration in the thawed high moisture content silts may be achieved only by use of a lower frequency radar, whereas in the sands and gravels greater depths may be detected with more sophisticated signal processing.
    Type of Medium: Series available for loan
    Pages: 16 Seiten , Illustrationen
    Series Statement: CRREL Report 83-11
    URL: https://apps.dtic.mil/docs/citations/ADA130225
    URL: https://hdl.handle.net/11681/9337
    Language: English
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  • 4
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    Morphology, hydraulics and sediment transport of an ice-covered river : field techniques and initial data (1986)
    Hanover, NH : U.S. Army Cold Regions Research and Engineering Laboratory
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    Call number: ZSP-201-86/11
    In: CRREL Report, 86-11
    Description / Table of Contents: This initial study of the ice-covered Tanana River, near Fairbanks, Alaska, attempted to 1) establish field methods for systematic and repetitive quantitative analyses of an ice-covered river's regime, 2) evaluate the instruments and equipment for sampling, and 3) obtain the initial data of a long-term study of ice cover effects on the morphology, hydraulics and sediment transport of a braided river. A methodology was established, and detailed measurements and samplings, including profiling by geophysical techniques, were conducted along cross sections of the river. A small, portable rotary drill rig equipped with a 356-mm (14-in.) ice auger was used to cut large diameter holes in the ice cover for through-the-ice measurements. Portable heat sources and a heated shelter were required to continuously thaw and dry equipment for the repetitive measurements. Measurements included ice cover thickness, water level, water depth, temperature, flow velocity, suspended load and bed load, frazil ice distribution and bed material composition. Remotely gathered data included apparent resistivity and subsurface radar profiling. The various techniques, sampling gear and problems encountered during use in the subfreezing cold are described in detail in this report.
    Type of Medium: Series available for loan
    Pages: v, 49 Seiten , Illustrationen
    Series Statement: CRREL Report 86-11
    URL: http://hdl.handle.net/11681/9318
    Language: English
    Note: CONTENTS Abstract Preface Introduction Study objectives and field locale Study site Equipment Vehicles Drilling equipment Sampling equipment Geophysical equipment Shelter and icing control Surveying equipment Miscellaneous equipment Field techniques and methodology Logistics Drilling procedures Data collection Geophysical analyses Experiences summary Morphology, transport and hydraulic data Mid-winter physical characteristics Hydraulic characteristics Sediment transport Late winter physical characteristics Seasonal morphology Geophysical data interpretation Spatial morphology Frazil ice characteristics Discussion and conclusions Recommendations Equipment Research Literature cited
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  • 5
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    Laboratory measurements of soil electric properties between 0.1 and 5 GHz (1982)
    Hanover, NH : U.S. Army Cold Regions Research and Engineering Laboratory
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    Call number: ZSP-201-82/10
    In: CRREL Report, 82-10
    Description / Table of Contents: Dielectric measurements have been performed on silt and sand samples from permafrost areas using Time Domain Reflectometry. The sample temperatures were varied from +25 °C to -25 °C, and volumetric water content was varied between oven-dry and 0.55 gH2O/cm3. The data were processed for frequencies between 0.1 and 5.0 GHz. The results show a constant K' and a low K' for frequencies up to 1 GHz. A frequency dependence seen on the data above 2 GHz is probably the result of unfrozen, adsorbed water. At moisture levels near saturation at all temperatures, these soils have excellent propagation characteristics for ground-probing radar operating below 0.3 GHz. Massive ice should be easily detectable in permafrost within a few degrees of 0 °C.
    Type of Medium: Series available for loan
    Pages: 7 Seiten , Illustrationen
    Series Statement: CRREL Report 82-10
    URL: https://hdl.handle.net/11681/9348
    Language: English
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  • 6
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    VHF electrical properties of frozen ground near Point Barrow, Alaska (1981)
    Hanover, NH : U.S. Army Cold Regions Research and Engineering Laboratory
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    Call number: ZSP-201-81/13
    In: CRREL Report, 81-13
    Description / Table of Contents: Electrical properties of frozen ground were measured using radio frequency interferometry (RFI) in the very high frequency (VHF) radiowave band. Ice-rich organic silts and sands and gravels of variable ice content were investigated during early April of both 1979 and 1980. Frequencies between 10 and 150 MHz were used with best results obtained between 40 and 100 MHz. Surface impedance and magnetic induction techniques were also used to obtain an independent measure of low frequency resistivity and to obtain a separate control on vertical inhomogeneity. Soil samples were tested for organic and water content. The dielectric constants determined for the ice-rich organic silts ranged from 4.0 to 5.5 while those for the sands and gravels were about 5.1. Dielectric loss was due to d.c. conduction and was very low for the silts but significant for the sands and gravels. The higher values for the sands and gravels were most likely due to the higher concentrations of salt that are reported to exist in the old beach ridges in this region. All the RFI measurements are believed to be indicative of only the first few meters of the ground although the radiowaves could penetrate to tens of meters.
    Type of Medium: Series available for loan
    Pages: iv, 18 Seiten , Illustrationen
    Series Statement: CRREL Report 81-13
    URL: https://hdl.handle.net/11681/9466
    Language: English
    Note: CONTENTS Abstract Preface Introduction Background Objectives and procedures Theory and instrumentation Radio frequency interferometry Case 1: Homogeneous ground model Case 2: Two-layer ground model RFI instrumentation Low frequency methods Point Barrow sites Results and discussion Site 1: Tundra Site 2: Beach ridge Site 3: Marsh Conclusions Literature cited Appendix A: Discussion of low-frequency geophysical methods
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  • 7
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    Radar detection of ice wedges in Alaska (1982)
    Hanover, NH : U.S. Army Cold Regions Research and Engineering Laboratory
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    Call number: ZSP-201-82/43
    In: CRREL Report, 82-43
    Description / Table of Contents: The radar signatures of ice wedges and wedge-like structures have been investigated for a variety of soil conditions. The radar used for this study emitted short sinusoidal pulses of about 10-ns duration with an approximate center frequency of 150 MHz. Most of the ice wedges existed at depths of about 1 m in a variety of silty and sandy soils with both frozen and thawed active layers. The position of the wedges was usually identified from corresponding surface features. An artificial ice wedge in coarse-grained alluvium was also profiled as well as wedge-like structures of fine silt in a coarse-grained glacial outwash. All wedges and wedge-like structures produced a hyperbolic reflection profile except when an active layer of thawed, saturated silt was present which eliminated returns from the wedges. The peaks of the hyper-bolas were sometimes masked by reflections from the permafrost table or other material interfaces, and multiple hyperbolas occurred at some sites. The dielectric constant of the host medium was often calculated from the linear portions of the hyperbolas and the results were verified by laboratory time domain reflectometry measurements per-formed on field samples. In some cases, hyperbolic profiles originated at several meters depth suggesting that deep ice wedges could be detected in areas of cold permafrost.
    Type of Medium: Series available for loan
    Pages: iv, 19 Seiten , Illustrationen
    Series Statement: CRREL Report 82-43
    URL: https://apps.dtic.mil/dtic/tr/fulltext/u2/a124571.pdf
    URL: https://hdl.handle.net/11681/9324
    Language: English
    Note: CONTENTS Abstract Preface Introduction Background Objectives and procedures Equipment used Radar TDR Definitions Massive ice Results Artificial wedge: Norwich, Vermont Ice wedges in sand: Fish Creek, Alaska Ice wedges: Prudhoe Bay, Alaska Ice wedges under thawed fine-grained soils: North Slope, Alaska Wedge-like soil structures: Ft. Greely, Alaska TDR measurements Summary and concluding remarks Literature cited Appendix A: Brief discussion of dispersion
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  • 8
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    Pulse transmission through frozen silt (1984)
    Hanover, NH : U.S. Army Cold Regions Research and Engineering Laboratory
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    Call number: ZSP-201-84/17
    In: CRREL Report, 84-17
    Description / Table of Contents: VHF-band radiowave short pulses were transmitted within the permafrost tunnel at Fox, Alaska, over distances between 2.2 and 10.5 m. The propagation medium was a frozen silt containing both disseminated and massive ice with temperatures varying from -7°C near the transmitter to probably -2 C near the center of the tunnel overburden. The short pulses underwent practically no dispersion in the coldest zones but did disperse and refract through the warmer overburden, as suggested by calculations of the effective dielectric constant. Most significantly the measured frequency content decreased as the effective dielectric constant increased. The results indicate that deep, cross-borehole pulse transmissions over distances greater than 10 m might be possible, especially when the ground is no warmer than -4°C. The information thus pined could be used for identifying major subsurface variations, including ground ice features.
    Type of Medium: Series available for loan
    Pages: ii, 14 Seiten , Illustrationen
    Series Statement: CRREL Report 84-17
    URL: https://apps.dtic.mil/dtic/tr/fulltext/u2/a147108.pdf
    URL: https://hdl.handle.net/11681/9519
    Language: English
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  • 9
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    Investigations of freshwater and ice surveying using short-pulse radar (1991)
    Hanover, NH : U.S. Army Cold Regions Research and Engineering Laboratory
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    Call number: ZSP-201-91/15
    In: CRREL Report, 91-15
    Description / Table of Contents: An overview is presented of recent activities and results in the use of commercially available short-pulse UHF radar for surveying ice conditions on freshwater bodies. Improvements in radar systems have made it possible to increase ice thickness resolution by as much as one third relative to that in past attempts, and some new signal processing approaches shown here may offer an order of magnitude improvement. Results from airborne surveying are shown in which the varieties of ice character are reflected. Given the lack of ground coupling, one can rely upon a reasonably well-defined wavelet structure for enhanced signal processing and interpretation possibilities. An algorithm is presented that locates returns from interfaces in the presence of noise for a non-minimum delay wavelet. The method performs a simple inversion in the frequency domain, enhanced by a time dependent weight designed to recognize the shape of the wavelet amplitude and phase spectra. Thin ice layers are resolved down to a few centimeters and are distinguished from an ice free condition by means of a matched filter system designed to recognize the interference pattern from parallel interfaces close to one another. The effects and constraints imposed by water layers on wet ice are discussed, as are general attenuation, sloping bottom, and critical angle effects in deeper water. In closing, observations on the problems and prospects of this sort of surveying are offered.
    Type of Medium: Series available for loan
    Pages: v, 31 Seiten , Illustrationen
    Series Statement: CRREL Report 91-15
    URL: https://hdl.handle.net/11681/9120
    Language: English
    Note: Contents Preface Nomenclature Introduction Field surveys Methods and paraphernalia Results Sloping bottom effects and critical angle phenomena Deconvolution and thin layers Well-separated echoes Thin ice layers Thin layers of water Observations Literature cited Abstract
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  • 10
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    Airborne resistivity and magnetometer survey in northern Maine for obtaining information on bedrock geology (1976)
    Hanover, NH : U.S. Army Cold Regions Research and Engineering Laboratory
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    Call number: ZSP-201-76/37
    In: CRREL Report, 76-37
    Description / Table of Contents: Geophysical studies were conducted during September and October of 1975 in northern Maine to locate rock types suitable for construction purposes for the proposed Dickey-Lincoln School Dam Project. Simultaneous airborne magnetometer and VLF electrical resistivity surveys were performed over an area of approximately 920 km2 surrounding the confluence of the St. John and Allagash rivers. The resulting data were used to construct contour maps of apparent resistivity and of total magnetic intensity above the earth's background magnetic field. During the same time period, ground and multi-elevation surveys were performed over a special test sector of known geology. The ground and airborne study in the test sector aided in interpretation of the data by revealing a strong correlation between igneous geology, resistivity, and magnetic intensity. Lack of a similar correlation between resistivity and magnetic data in the remainder of the survey area suggested an absence of additional areas of igneous rocks. The multi-elevation survey of the test area indicated that changes in flight altitude, necessitated by the topographic relief encountered, would not seriously affect the regional resistivity patterns. Although there was no strong evidence of igneous rocks outside the test sector, suitable rock types may exist within the Dss geologic unit (cyclically bedded gray slate and sandstone) in the central part of the main survey area, where most of the high resistivity contours occur.
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    Pages: v, 24 Seiten , Illustrationen
    Series Statement: CRREL Report 76-37
    URL: https://hdl.handle.net/11681/9530
    Language: English
    Note: CONTENTS Abstract Preface Summary Introduction Measurement techniques employed Ground Airborne Magnetometer survey Results Ground control study VLF survey Bedrock geology and resistivity Aeromagnetic survey results Conclusions Literature cited Appendix A. Theory of electromagnetic resistivity surveying Appendix B. Magnetic surveying
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