Ice jacking

Ice jacking occurs when water invades a confined space in a structural support or geologic formation, and upon freezing causes structural fracture as the ice expands.[1] Ice jacking is a continuous process during the winter in areas that are located by lakes. The process starts when the ice begins to crack followed by water filling in those gaps and the process continues until there is a wall of ice surrounding the lakes shoreline, sometimes reaching up to three feet. The formation of ice jacking allows for nutrients to get trapped in the ice creating organic fertilizer to create a buffer (transition between land and aquatic organisms) which collaborates with already existing plants on the shore line that contribute to the development of future organisms leading to the expansion of fish.[2] However ice jacking is unfeasible due to the lack of control over it. There are no methods that will prevent damages from ice jacking but there are a few defenses that can be used to fight against ice jacking such as building a riprap along the shoreline, attack its strengths/weaknesses, allow the natural process to take place and repair the damages later, or do nothing at all and let nature take its course.[3]


One difference between ice jacking and ice heaving is that ice jacking occurs in the middle of winter while ice heaving occurs in the early spring. When there is snow, the ice stays at constant temperature. When there is no snow, nothing can protect or cover the ice from the changing ambient temperatures. When the temperature decreases, the ice will contract which causes cracks to occur in the ice which later then are filled with the water from below. The ice expands once the temperature rises and the ice pushes up towards the shoreline since it does not have anywhere else to go. More pressure is put on the shoreline as the ice is jacked towards the shoreline. A solution to ice jacking should consist of sand shoreline. [4]

Geologic engineering

Rock slope failures can occur due to the presence of water; ice jacking occurs when water between joint or fissure surfaces freezes and expands. This type of failure is progressive, resulting in incremental weakening over time, often requiring several cycles before failure.[5] Ice jacking is one form of rock erosion. In a 2005 study, middle size rock falls (10 to 100,000 m3) in the French Subalpine Ranges in an elevation ranging from 200 meters and 2000 meters above sea level were observed. Statistical analysis studied the triggering factors of 46 rock falls, investigating the rainfall, freeze-thaw cycles, and earthquakes in the region. Correlation was found between failure and freeze-thaw cycles, suggesting that ice jacking is a main triggering factor in rock falls.[6]

For example, on December 17, 2008 a Gondola tower on Blackcomb Mountain in Whistler, B.C collapsed as a result of ice jacking. The splice broke when the water entered into a section of the fourth tower and began to expand. This occurred around 2:30 pm, and left over fifty passengers stranded in sub-zero temperatures for hours. All of the passengers stuck in cabins on the Excalibur Gondola lift were rescued, with only twelve suffering from mild injuries. Many passengers recall watching in horror as the cars swung sideways, one dangling above the creek. It was apparent the first cabin to fall took the hardest hit, falling violently to the ground. Reports state none of the cabins actually came off of the cable, but that the strength of the cable had been significantly compromised. Following the incident, lift maintenance teams conducted inspections of all other towers to make sure there would be no other occurrence of ice jacking. After a second inspection by the British Columbia Safety Authority (BCSA), the lift were given approval to perform regularly again.[7]

See also

References

  1. ↑ Whistler reopens as officials blame ice damage for collapsed tower
  2. ↑ Rufer, Moriya. "The tremendous power of lake ice".
  3. ↑ Paul, Gerald L. "ICE POWER". The damage ice-Jacking can do.
  4. ↑ "Your Shoreline's Top 3 Enemies". Lakeshore Guys.
  5. ↑ Xanthakos, Petros P.; Abramson, Lee W.; Bruce, Donald A. (1994). Ground Control and Improvement. New York: John Wiley. p. 737. ISBN 9780471552314.
  6. ↑ "Failure mechanisms and triggering factors in calcareous cliffs of the Subalpine Ranges (French Alps)". ScienceDirect. doi:10.1016/j.enggeo.2006.05.009.
  7. ↑ "Ice-Jacking Caused B.C. Gondola Tower Collapse". CTV News Vancouver.


This article is issued from Wikipedia. The text is licensed under Creative Commons - Attribution - Sharealike. Additional terms may apply for the media files.