Ninth International Conference on Permafrost ... - IARC Research

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Non-Linear Analysis of the Thermal Characteristics of Permafrost Embankmentwith Crushed-Rock Revetment and Insulation on Qinghai-Tibet PlateauMingyi Zhang, Shuangyang Li, Shujuan Zhang, Yuanhong DongState Key Laboratory of Frozen Soil Engineering, Cold and Arid Regions Environmental and Engineering Research Institute,Chinese Academy of Sciences, Lanzhou 730000, ChinaIntroductionThe embankment with crushed-rock revetment hasbeen widely used in the construction of the Qinghai-Tibetrailway/highway and is an effective measure to ensure thethermal stability of permafrost embankment (Lai et al. 2003,2004, Sun et al. 2004, Ma et al. 2002); however, becauseof the influence of global warming, it is difficult to protectthe underlying permafrost from warming, even thawing(Wang et al. 1996). Therefore, in order to sufficiently protectthe underlying permafrost, a numerical representation ofthe unsteady two-dimensional continuity, momentum, andenergy equations of thermal convection for incompressiblefluid in porous media (Nield et al. 1999, Kong et al. 2002) isused to analyze and compare the temperature characteristicsof the embankments with crushed-rock revetment, with andwithout insulation, under the global warming in this study.Results and DiscussionsBased on the temperature and geology conditions on theQinghai-Tibet Plateau (Cheng et al. 2003, Zhu et al. 1988,Qin, 2002, Lai et al. 2003), the temperature distributions ofthe three embankment models with crushed-rock revetment,with and without insulation (Fig. 1), constructed on July 15,are simulated and analyzed for 50 years.Figure 2 is the temperature distribution of the embankmentwith crushed-rock revetment (1.60 m thick), withoutinsulation on October 15, after 50 years of the construction. Itcan be seen from this figure that the location of the permafrosttable (0°C isotherm) is y = -2.39 m under the natural groundsurface, while that is y = -1.79 m in the centerline of theembankment and 0.60 m higher than that under the naturalground surface; furthermore, -0.2°C isotherm is high underthe slope foot of the embankment, while low in the middleof embankment.Figure 3 shows the temperature distribution of theembankment with crushed-rock revetment (2.0 m thick),without insulation on October 15, after 50 years of theconstruction. From this figure, we find that the groundtemperature distribution is similar to the embankment withcrushed-rock revetment (1.60 m thick), without insulation(Fig. 1). In detail, the permafrost table (0°C isotherm)is y = -2.39 m under the ground surface, while that is y =-1.69 m and 0.03 m in the centerline and side slope of theembankment, respectively.Based on the above the analyses, we can conclude thatthe embankments with crushed-rock revetment withoutinsulation have an active cooling effect on the underlyingpermafrost, but cannot effectively reduce the underlyingground temperature. Furthermore, their cooling effects arestrongest at the side slope foot, but weak in the middle. WeY(m)420-2-4-6-8-10-20 -15 -10 -5 0X(m)Figure 2. Temperature distribution of the embankment with crushedrockrevetment (1.60 m thick), without insulation on October 15,after 50 years of the construction (Unit: °C)4A30.0mB1:1.5B'CdC'' DE1:1.750.8m7.2m3.4mF5.0m0.4mG H''InsulationHCrushed-rock revetment30.0mI' I JY(m)20-2-43.0mNK-6MFigure 1. Embankment model with crushed-rock revetment.L30.0m-8-10-20 -15 -10 -5 0X(m)Figure 3. Temperature distribution of the embankment with crushedrockrevetment (2.0 m thick) without insulation on October 15,after 50 years of the construction (Unit: °C).359
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 tY(m)420-2-4-6-8-10-20 -15 -10 -5 0X(m)Figure 4. Temperature distribution of the embankment withcrushed-rock revetment (1.6 m thick) and insulation on October15, after 50 years of the construction (Unit: °C).also find that when the thickness of a crushed-rock revetmentreaches a certain value, its cooling effect on the middle partof embankment cannot be effectively increased by adding itsthickness only.Therefore, we propose the embankment with crushedrockrevetment (1.60 m thick) and insulation, namely, addinsulation at the upside of the embankment with crushedrockrevetment.Figure 4 is the temperature distribution of the embankmentwith crushed-rock revetment (1.6 m thick) and insulation onOctober 15, after 50 years of the construction. It can be seenfrom this figure that the permafrost table (0°C isotherm)is y = -2.39 m under the ground surface, while that is y =0.05 m and 0.92 m in the centerline and side slope of theembankment, respectively. Furthermore, the temperatureunder the embankment is lower than those under the abovetwo embankments without insulation (Figs. 1, 2), and -0.3°Cisotherm still exists under the embankment. This shows thatthe embankment with crushed-rock revetment and insulationnot only can raise the permafrost table, but also reduce theunderlying permafrost temperature.Therefore, it is proposed that, in warm permafrost regions,insulation should be used to increase the cooling effectof embankment with crushed-rock revetment; however,the insulation must be paved in the upper portion of theembankment.Kong, X.Y. & Wu, J.B. 2002. A bifurcation study of non-Darcy free convection in porous media. ActaMechanica Sinica 34(2): 177-185.Lai, Y.M., Li, J.J., Niu, F.J. et al. 2003. Nonlinear thermalanalysis for Qing-Tibet Railway embankments incold regions. Journal of Cold Regions Engineering17(4): 171-184.Lai, Y.M., Zhang, S.J., Zhang, L.X. et al. 2004. Adjustingtemperature distribution under the south and northslopes of embankment in permafrost regions by theripped-rock revetment. Cold Regions Science andTechnology 39(1): 67-79.Ma, W., Cheng, G.D. & Wu, Q.B. 2002. Preliminary studyon technology of cooling foundation in permafrostregions. Journal of Glaciology and Geocryology24(5): 579-587.Nield, D.A. & Bejan, A. 1999. Convection in Porous Media,2 nd ed. New York: Springer-Verlag.Qin, D.H. 2002. The Comprehensive Evaluating Report onthe Environment Evolvement in West China. Beijing:Science Press.Sun, Z.Z., Ma, W. & Li, D.Q. 2004. Experimental study onthe cooling effect air convection embankment crushedrock slope protection in permafrost regions. Journalof Glaciology and Geocryology 26(4): 435-439.Wang, S.L., Zhao, X.F., Guo, D.X. et al. 1996. Response ofpermafrost to climate changes in the Qinghai-XizangPlateau. Journal of Glaciology and Geocryology 18(suppl): 157-167.Zhu, L.N. 1988. Study of the adherent layer on differenttypes of ground in permafrost regions on theQinghai-Xizang Plateau. Journal of Glaciology andGeocryology 10(1): 8-14.AcknowledgmentsThis research was supported by the National NaturalScience Foundation of China (Grant No. 40601023 and40730736), the Knowledge Innovation Important Programof the Chinese Academy of Sciences (Grant No. KZCX3-SW-351).ReferencesCheng, G.D., Jiang, H., Wang, K.L., et al. 2003. Thawingindex and freezing index on the embankment surfacein permafrost regions. Journal of Glaciology andGeocryology 25(6): 603-607.360
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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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xvi
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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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