Ice jacking

Ice jacking occurs when water permeates a confined space within structural support or geological formation causing structural fracture as the ice expands when it freezes.[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, which is followed by water filling in those gaps and the process continues until there is a wall of ice surrounding the lake's shoreline, sometimes reaching up to three feet. The formation of ice jacking allows for nutrients to get trapped in the ice, creating organic fertilizer. This creates a buffer (transition between land and aquatic organisms) which collaborates with already existing plants on the shoreline that contribute to the development of future organisms and lead to the expansion of fish.[2] However, ice jacking is impractical due to the lack of control over the process. There are no methods that will prevent damage 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 or allowing the natural process to take place and either repairing the damage or allowing the affected areas to remain damaged.[3]

There are multiple terms that are sometimes referred to as ice jacking such as ice shove, ice heaving, otherwise known as frost heaving, and ice wedging. One difference between ice jacking and ice heaving is that ice jacking occurs in the middle of winter, whereas ice heaving occurs in early spring. When there is snow, the ice stays at a 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 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 as a result of ice jacking due to the presence of water in joints or fissure surfaces. 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. A correlation was found between failure and freeze-thaw cycles, suggesting that ice jacking is a major triggering factor in rock falls.[6]

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 more than 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. Although some of the cabins fell, reports state none of the cabins 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 was given the approval to perform regularly again.[7]

See also
  • Frost weathering – Mechanical weathering processes induced by the freezing of water into ice
  • Oxide jacking – Damage to stone caused by the oxidation of embedded metal

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. Frayssines, M.; Hantz, D. (2006-08-25). "Failure mechanisms and triggering factors in calcareous cliffs of the Subalpine Ranges (French Alps)". Engineering Geology. 86 (4): 256–270. CiteSeerX 10.1.1.382.9102. doi:10.1016/j.enggeo.2006.05.009.
  7. "Ice-Jacking Caused B.C. Gondola Tower Collapse". CTV News Vancouver.
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