permafrost
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Problem And Solutions In Design Of Problem And Solutions In Design Of
Roadway And Railway Network In Permafrost RegionRoadway And Railway Network In Permafrost Region
A Seminar on
By
Ashish PariharRoll no. 141701
M.Tech. (Transportation Engineering)
Overview• What is Permafrost?• Where Permafrost?• Why does permafrost thaw?• What happens when permafrost thaws?• Key Terms and Landforms• Case Study• Engineered Solutions• Summary• References 02/18/15 1
What is Permafrost?
Soil or rock that remains below 0°C throughout the year, or may be for two
or more years.
Ice is not always present, frequently occurs
Moisture in the form of either water or ice may or may not be present.
Permafrost may therefore be unfrozen, partially frozen, or frozen
depending on the state of the ice/water content.02/18/15 2
What is Permafrost?
PermafrostPermafrost
Source: http://wiki.fis-ski.com/index.php/Permafrost
02/18/15 3
Where Permafrost? North America
Scandinavia
Russia
China
Some Estimated Depth:
• 440 m in Barrow, Alaska
• 600 m in the Canadian Arctic Islands
• 1493 m in the northern Lena and Yana
River basins in Siberia02/18/15 4
Why Does Permafrost Thaws?
Changes occur due to:
oSoil compression,
oChanging drainage of soil,
oClimatic changes,
oTemperature changes
Solar heating of the surface,
Temperature of pavement
surface,
Source: http://www.scienceinschool.org/2012/issue22/permafrost02/18/15 5
“No ground to stand on”
Travel Problems Increasing road hazards & damage Shorter travel season Railways shift and bend Airport runways crack
More Geohazards Landslides, Debris & mud flows Subsidence
Source: http://wiki.fis-ski.com/thawingeffects.php02/18/15 6
• Permafrost:
• Continuous Permafrost:
• Discontinuous Permafrost:
Permanently frozen ground
Temperatures have remained below 0 °C for at least 2 years
Mean annual air temperatures of below -5 °C all year,
as low as -50 °C.
Slightly warmer areas
Islands of permanently frozen ground separated by small pockets of unfrozen less cold areas.
Mean annual temps of between -1 °C and -5 °C
Key Terms And LandformsKey Terms And Landforms
02/18/15 7
Source: http://www.scienceinschool.org/2012/issue22/permafrost
Key Terms And LandformsKey Terms And Landforms
02/18/15 8
Summer temperatures sufficient to melt
This layer can be very mobile
It varies in thickness depending on latitude and vegetation cover.
Any unfrozen material within the permafrost zone.
• Active layer:
• Talik:
Key Terms And LandformsKey Terms And Landforms
02/18/15 9
Case Study
Source: http://www.chinatibettrain.com/aboutus.htm02/18/15 10
China Railway Line
QINGZANG ( Qinghai - Tibet) Railway nearly 1200 mile
Stations name :- Xining to Lhasa
Approximately 1300 miles of the new railway in between Golmud to Lhasa was having
Continuous
Discontinuous Permafrost
02/18/15 11
Engineered Solutions
1) Active method : To destroy
permafrost section completely.
2) Passive method : It Functions to
reduce heat absorption.
02/18/15 12
• Thermo-Syphon• Ventiduct Embankments• Air-Cooled Stone Embankment• Awning/ Shading Boards• Expanded Polystyrene Insulation• Dry Bridges
Engineered Solutions
02/18/15 13
Thermo-Syphons Pressurized Cylindrical tube and
Filled of low boiling point.
Dissipation of heat by:
Evaporation
Condensation of liquid.
These are best utilized for high risk sides
Unstable permafrost.Source: http://info.tibet.cn/en/news/phn/pnt/t20060605_120583.htm
02/18/15 14
Thermo-Syphons
Source: https://www.thermalfluidscentral.org/encyclopedia/index.php/Two-Phase_Closed_Thermosyphon
02/18/15 15
Ventiduct Embankments
Inclusion of pipes serving as air culverts .
Can increase heat absorption with in the embankment.
Requires natural wind current to remove heat from the
embankment.
Source: http://info.tibet.cn/en/news/phn/pnt/t20060605_120583.htm
02/18/15 16
Air Cooled Stone Embankments
Poorly graded aggregates are used to create pore spaces.
Rock layer act as thermal insulating barrier
Block stone embankments utilize large aggregates
Roughly 8-12 inches in diameter
Crushed rock embankments use smaller aggregates
3-4 inches in diameter.
Source: http://wiki.fis-ski.com/index.php/heat_transfer
17
Rock Embankment Configurations
Air Cooled Stone Embankments
Source: http://info.tibet.cn/en/news/embkmnt/pnt/t20060605_120583.htm
02/18/15 18
Awnings And Shading Boards
Primary function Is to reduce solar radiations.
Water infiltration and snow accumulation are minimized.
Source: http://www.scienceinschool.org/2012/issue22/permafrost/awnings_shading.htm
02/18/15 19
Awning
Awning configurations02/18/15 20
Dry Bridges
Pile lengths of 25 to 30 m,
Pile diameters of about 1.2m,
Utilizes a negative friction force
To ensure engineering stability,
Ignoring the carrying capacity of pile
Permafrost thaw problems. Er’a’ga dry bridge on Muli Railway, China
Source: http://wiki.fis-ski.com/index.php/Permafrost
02/18/15 21
SUMMARY OF ENGINEERED SOLUTIONSEngineered
SolutionExpected Outcome Potential Drawbacks
Cost ($/100 track feet)
Thermosyphons
High risk sites, unstable permafrost, useful for transitional zones
Damage during transport or installation, obstruction of fins, maintenance potential
$27,500-$30,800
Ventiducts
Embankments
Minimize differential settlements, reduce internal temperature of embankment
Blockage due to snow or debris, minimized performance due to settlements, water ponding, maintenance potential
$9,800- PVC
$16,500- Concrete
$23,750- Metal
Block Stone
Embankments
Increase convection cooling of entire embankment, increased full width embankment stability
Plugging due to snow or fines, settlements risk $44,800
Crushed Rock
Revetments
Convection cooling of shoulders, stability of shoulder sections
Warming in centre of embankment with cooling of shoulders (differential settlement), plugging due to snow or fines
$12,000 22
SUMMARY OF ENGINEERED SOLUTIONS
Engineered Solution
Expected Outcome Potential DrawbacksCost ($/100 track
feet)
Awning/
Shading Board
Reduce solar radiation, minimize water infiltration, improve convection cooling
Damage due to natural or manmade occurrences, maintenance potential
No Data
Extruded
Polystyrene
Minimize heat influx into soil, reduce frost penetration depth, minimize construction depth
Water absorption, mechanical damage, decreasing insulation performance $2,300
Dry Bridge
Ensure stability during permafrost degradation, eliminates settlements and thaw consolidation
Differential settlements of columns, damages due to natural or manmade occurrences $1,040,000
23
Summary
Should be part of the planning of any engineering project in the north.
It is best to disturb the permafrost.
Thawing make soils more stable for future construction.
Costs of continual maintenance vs. initial cost of advanced
engineering solutions
How rapidly can permafrost thawing be expected to occur?
Special attention has been paid to ground temperature and ice
content.24
References
Cheng, G. D. _1984_. “Problems on zonation of high-altitude permafrost.” Acta Geogr. Sin., 39_2_, 185–193 _in Chinese; Abstract in English_.
Cheng, G. D. _2003_. “The effect of local factors on spatial distribution of permafrost and its revealing to Qinghai–Xizang Railroad design.” Sci. China (Ser. D), 33_6_, 602–607.
Cheng G. D. _2005_. “A roadbed cooling approach for the construction of Qinghai–Tibet Railway.” Cold Regions Sci. Technol., 42_2_, 169–176.
Ding, Y. J. _1998_. “Recent degradation of permafrost in China and the response to climate warming.” Proc., 7th Int. Conf. on Permafrost, Univ. of Laval, Yellowknife, Canada, 225–230.
Lai, Y. M., Zhang, L. X., and Zhang, S. J. _2003_. “The cooling effect of ripped-stone embankments on Qinghai–Tibet Railway under climatic warming.” Chin. Sci. Bull., 48_6_, 598–604.
Research Group of the Qinghai–Xizang Highway. _1983_. “Distribution regularities of high-ice-content permafrost along Qinghai–Xizang Highway.” Proc., 2nd National Conf. on Permafrost, Gansu Cultural Press, Lanzhou, China, 43–51.
02/18/15 25
References
Tong, C. J., and Wu, Q. B. _1996_. “The effect of climate warming on the Qinghai–Tibet Highway.” Cold Regions Sci. Technol., 24_1_, 101–106.
Wang, S. L., Zhao, X. F., Guo, D. X., and Huang, Y. Z. _1996_. “Response of permafrost to climate change in the Qinghai–Xizang Plateau.” J. Glaciol. Geocryol., 18 _Special Issue_, 157–165 _in Chinese_.
Wu, Q. B., Liu, Y. Z., and Tong, C. J. _2003_. “Interaction between frozen soil and engineering in cold regions.” J. Eng. Geol., 8_3_, 281–287.
Sheng, Y., et al. ~2002b! “Application of thermal-insulation treatment to roadway engineering in permafrost region.” J. Glaciol. Geocryol., 24~5!, 618–622.
Slater, A. G., Pitman, A. J., and Desborough, C. E. ~1998!. “Simulation of freeze-thaw cycles in a circulation model land surface scheme.” J. Geophys. Res., [Atmos.], 103~D10!, 11303–11312.
Smith, M. W., and Riseborough, D. W. ~1996! “Permafrost monitoring and detection of climate change.” Permafrost Periglacial Process., 7~4! 301–309.
02/18/15 26
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