Ninth International Conference on Permafrost ... - IARC Research

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Application of Georadar in the Cryosphere for the Study ofEngineering ConstructionsSergey VelikinViluy Permafrost Station of the Permafrost Institute, RAS Siberian Branch, ChernishevskiiRudolf CzhanPermafrost Institute, RAS Siberian Branch, Yakutsk0 20 m 0 20 m0248ma) b) noise from air electric mainFigure 1. An example of a small air stratum effect (4 cm) betweenthe bottom of antenna (facility SIR2000 antenna FGMOD5106, f =200 MHz) and probing surface (concrete-surfaced road on frozenfoundation): a) georadarogramm with antenna without air-gap (nosupport); b) georadarogramm with uplifted antenna (4 cm air-gapdue to support on wheels)..002004006004.050 100 1503.45.15.1 6.46.4.. .m 06.750 100 150800 ns6.7 Depth of reflectors in metersFigure 2. Georadar observation from the ice sheet of Sitikanreservoir (bottom sediments study). On the left: GPR observationafter ice cleaning from sleet mixed with road dust.The ground-penetrating radar (GPR) method is veryuseful for the study and monitoring of different engineeringconstructions foundation beds. The advantages of GPRare mobility, compactness, and possibility of continuousobservation. The results of a GPR survey with different daysurface preparations—cleaning, surfacing, wettings—arepresented. Seasonal peculiarities of the state of groundsections were also taken into consideration for GPR datainterpretation. This approach, in some cases, improvesthe effectiveness of GPR surveys performed in WesternYakutia.The effectiveness of the GPR method for the study anddiagnosis of engineering constructions foundation beds canbe improved as a result of special day surface preparation(cleaning, surfacing, and wetting) before survey. The otherfactor of GPR data improvement is seasonal observations(Judge at al. 1991). A priori information about lithology ofsections, changes of temperature condition in basement soils,and temperatures of the beginning of thawing-freezing givesa key to the effective use of GPR technologies for the studyand control of engineering constructions, buildings, and roadcoverings. Use of georadar sections difference observablein winter and summer time, before and after precipitations,that is, in various temperature-moisture conditions, is veryinformative (Velikin at al. 2000).Figure 1 shows the result of a GPR survey along a road witha concrete covering. Measurements were carried out with thesame equipment at a present small air-gap (4 cm) between thebottom of the antenna and road (measurements on a supportwith wheels) and without it (shooting without a support). Asshown in Figure 1, in the case of measurements, an antennaradarogramma raised above the road is considerably noisy incomparison with the results of observation without a supportthat complicates section study.After clearing road dirt from along the top of Sitikanreservoir dam, GPR data revealed rather detailed elementsof the dam structure. Knowledge of the positions of therevealed elements allows supervision of the state of Sitikandam while conducting building actions (strengthening ofa road cloth, cementation of embanked sections weakenedduring object exploitation). Figure 2 shows the result onGPR data quality of cleaning the Sitikan reservoir ice sheet.After cleaning, the noise level becomes much lower. Thesedata were used for proper determination of the thickness ofthe underwater part of bank slope anti-seepage filling.It is important to note that cleaning and smoothing ofsounding surfaces sharply improves radarogramm qualitydue to reduction of the influence of microrelief and a nonuniformcovering of study sites with dirt and sleet, whichcan considerably deform and attenuate signals.Figure 3 presents GPR mapping of the productive horizonbasement and reveals details of its structure. This becomespossible only after removal of the soil-vegetative layer,which was a strong screen because of high humidity andpresence of a clay sheet.Among other measures on preparation of probing surfaces,it is necessary to note filling with a fine-grained material andsmoothing of a surface of studied structures. In particularat one of the dams in western Yakutia, it revealed with highresolution a weakened zone and a filtration window in thebody of the dam (Fig. 4).During a georadar survey, good effect gives the use ofseasonal and weather factors; that is, sounding in freezingand thawing conditions of investigated sections, before andafter surface wetting by rainfall.m329
Ni n t h In t e r n at i o n a l Co n f e r e n c e o n Pe r m a f r o s t06.5 m06.5 m0 100 200 300 m0 150 m 0 150 m024810MBedding rocks roof boundary(1, 2, 3 – different soils of terrace sediments)Figure 3. Georadar plot of diamond alluvial deposit from diamondfieldin Western Yakutia: a) radarogramm after preliminaryprocessing; b) radarogramm with picked geoelectric horizonscorresponding to different soils of terrace sediments.Figure 4. Radarogramm along coping of settling pound. Detectingseepage zone in the body of dam. 1: outline of deconsolidationsink; 2: seepage zone. On the right, road-covered wet mud withbroken stone. On the left, road after preparation.In December 2005 and February 2006, GPR seasonalsurveys were performed on a diamond alluvial depositduring winter frost penetration time. It appeared that, inDecember, the maximum frost penetration and summermaximum thaw depth rather precisely marked out, whichhas proved to be true by temperature observations. Furtherin January–February, during further freezing of a section,lithological borders, including the roof and bottom of theproductive horizon, distinctly stand out on the radarogramm,which proves to be true by the geological data on cores anddescription of a prospecting shaft. During processing, theaccount of a relief of a daytime surface has been carried out,and it has revealed confidently the bottom of the productivehorizon, to define its depth and thickness for the momentof the beginning dragging works. Consequently, it waspossible to predict the state of soils developed section (timeof thawing of productive horizon after filling dragging afoundation trench).ConclusionThe results presented in our work show that duringgeoradar survey, application of different types of preparationof studied surfaces (cleaning, filling, smoothing, wetting,etc.), as well as using and accounting seasonal- climatic andweather factors, allows productivity increase of GPR surveyin many cases.In spite of that, in a basis of georadar survey is differenceof rocks and soils in dielectric permittivity and electroconductivity, the basic character of georadar sections lays, asa rule, reflects mainly lithological boundaries (Finkelshtein etal. 1977, Vladov & Starovoitov 2005). Boundaries associatedwith the geocryological state frequently have a secondarycharacter and come to light on a radarogramm less precisely.In many cases, basic elements of geocryological structurecome to light more brightly during the periods which are notcorresponding seasonal geocryological state. In particular, itconcerns the boundary of maximal seasonal thawing duringintensive freezing.ReferencesFinkelshtein, M.I., Mendelson, V.L. & Kuteev, V.A. 1977.Radar-Location of Layered Terrestrial Covers.Moscow: Soviet Radio, 176 pp. (in Russian).Judge, A.S., Tucker, C.M., Pilon, J.A. & Moorman, B.J.1991. Remote Sensing of Permafrost by Ground-Penetrating Radar at Two Airports in Arctic Canada.Arctic 44 Supp. 1: 4-48.Velikin, S.A., Vladov, M.M. & Makcheeva, I.V. 2000.Application georadiolocation method for the study ofhydro units in permafrost conditions. In: Georadar inRussia-2000. Moscow, MGU: 36-38.Vladov, M.M. & Starovoitov, A.V. 2005. Introductionto georadiolocation. Moscow: MGU, 165 pp. (inRussian).330
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NICOP 2008 Ninth <
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ContentsPreface ...................
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Mapping and Modeling the Distributi
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Satellite Observations of Frozen Gr
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xiiIce Wedge Thermal Regime in Nort
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xivPermafrost Response to Dynamics
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NICOP SponsorsUniversitiesUniversit
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Deep Permafrost Studies at the Lupi
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Effect of Fire on Pond Dynamics in
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Cryological Status of Russian Soils
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Acoustical Surveys of Methane Plume
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Permafrost Delineation Near Fairban
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Preparatory Work for a Permanent Ge
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A Provisional Soil Map of the Trans
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Martian Permafrost Depths from Orbi
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Time Series Analyses of Active Micr
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Impact of Permafrost Degradation on
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DC Resistivity Soundings Across a P
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Modeling Thermal and Moisture Regim
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A Provisional Permafrost Map of the
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Alpine Permafrost Distribution at M
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Cryogenic Formations of the Caucasu
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Modeling Potential Climatic Change
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A Hypothesis: A Condition of Growth
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Modeled Continual Surface Water Sto
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Freeze/Thaw Properties of Tundra So
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Discontinuous Permafrost Distributi
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Thermal Regime Within an Arctic Was
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Seasonal and Interannual Variabilit
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Twelve-Year Thaw Progression Data f
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Continued Permafrost Warming in Nor
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Landsliding Following Forest Fire o
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A Permafrost Model Incorporating Dy
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Seasonal Sources of Soil Respiratio
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Greenland Permafrost Temperature Si
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The Importance of Snow Cover Evolut
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The Account of Long-Term Air Temper
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The Combined Isotopic Analysis of L
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Adaptating and Managing Nunavik’s
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Human Experience of Cryospheric Cha
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HiRISE Observations of Fractured Mo
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A Soil Freeze-Thaw Model Through th
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Mapping and Modeling the Distributi
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First Results of Ground Surface Tem
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Historical Changes in the Seasonall
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Rock Glaciers in the Kåfjord Area,
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Snowpack Evolution on Permafrost, N
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Climate Change in Permafrost Region
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Maximizing Construction Season in a
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Pleistocene Sand-Wedge, Composite-W
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Ninth International Conference on Permafrost ... - IARC Research

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