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Unstable Leda Clay & Risk of Sinkholes or Landslides
in Quebec & Eastern Ontario, Canada, Norway, & Sweden
- POST a QUESTION or COMMENT about sinkholes & landslides & the Leda Clay formations in Quebec & Ontario Canada & in Norway & Sweden
This article describes sinkholes caused by Quick clay or Leda clay hazards in Quebec & Ontario and also discusses the relationship between sinkholes and clay soils causing landslides, soil subsidences, or sudden sinkholes in Canada, Norway, Sweden.
This article series explains what sinkholes are and why they occur, describes their effects on buildings, and gives building and site inspection advice useful in identifying areas where there is an increased risk of sink holes at properties.
Synonyms and similar terms for sink holes include: shake hole, swallow hole, swallet, doline, cenote, moulin, and glacier mill, unstable clay soil, Leda clay, or quick clay.
The Lemieux landslide photo (left) of an earlier unstable clay soil or quick clay landslide is from the Canadian Department of Natural Resources.
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Sinkholes in Canada- Leda Clay (Quick Clay) in Quebec & Eastern Ontario, also in Norway & Sweden
Unstable clay soils found in some areas of Quebec and eastern Ontario (also found in Rissa, Norway) can "spontaneously liquefy with little or no provocation", leading to sudden catastrophic sinkhole formation and soil collapse reported the New York Times 13 May 2010).
Readers who find evidence of an active sinkhole should see SINKHOLES - IMMEDIATE SAFETY ACTIONS.
The bare minimum that a property owner needs to know about sinkholes or any other sudden subsidence of soils at a property is that these conditions might be very dangerous. Someone falling into a sink hole or into a collapsing septic tank could be seriously injured or even die.
If a suspicious hole, subsidence, or depression appears at a property the owner should rope off and prevent access to the area to prevent anyone from falling into the opening, and then should seek prompt assistance from a qualified expert, geotechnical engineer, septic contractor, excavator, or the like.
Sinkholes hundreds of feet in diameter have occurred in Eastern Canada, Florida, and Texas - big enough to swallow a home. The "December Giant" sinkhole in Montevallo, Alabama was 520 x 125' and 60' deep. The Dasietta Texas sinkhole reached 525' x 600' and a depth of 150', collapsing an era of roughly 1/10 of a square mile within two days of its first appearance.
The Times article reports the tragic death of the Richard Préfontaine family when on May 11, 2010 their home suddenly fell into a mud crater 100 feet deep hole approximately 900 feet by 1700 feet in size. More than 250 such collapses have been identified in this area of Canada.
The Lemieux landslide photo (left) of an earlier unstable clay soil or quick clay landslide is from the Canadian Department of Natural Resources.
The May 2010 Times article explained that because the unstable clay formed in salt water the molecular structure of its particles is unstable (compared with clays formed as layers in fresh water). When an event breaks the molecular bonds between clay particles the clay can spontaneously liquefy.
Skölda et als. reported on the chemistry of unstable clay soils in 2005. In 1950 in Surte, Southwest Sweden, unstable "quick clay" soils led to a catastrophic soil collapse as well. Our photo (left) of the 1950 landslide in Surte is from Wikimedia Commons.
The same Times article reported another clay liquefication collapse in St. Jean Vianney, Quebec in 1971, when 31 people died and 40 homes were destroyed, and continued that the town of Lemieux, Ontario (east of Ottawa) was relocated in 1991 due to concern for unstable clay soils that two years later collapsed over a 42-acre area.
According to Canada's Department of Natural Resources, "The most disastrous Leda clay landslide in eastern Canada occurred in 1908 at Notre-Dame-de-la-Salette, Quebec, with the loss of 33 lives."
This "quick clay" or "Leda clay" found in Quebec and Eastern Ontario is a unique marine clay that can sudden liquefy when disturbed. Quick clay / Leda clay may appear to be solid ground, but it is composed of as much as 80 percent water whose clay particles are held together primarily by the surface tension of water itself.
As for some of the other types and locations of sinkholes discussed here, the presence of un-stable quick clay in Eastern Canada can be detected by soil testing but not by casual inspection of the top layer of (more stable) ground soils. However the long history of more than 100 years of documented sudden subsidences in areas of Quebec has made local experts aware of the risk of this dangerous soil.
Similar unstable clay soils or quick clay found in Rissa, Norway, led to an April 1978 soil collapse covering more than 330,000 squre meters.
Significant quick clay or Leda clay collapses in Eastern Canada have been documented in 1908, 1955, 1971, [and April 1978 in Rissa, Norway, 330,000 sq. meters] as well as soil tests (and town relocations) in 1989, 1991, 1993, and the 2010 catastrophe and deaths reported above.
The map (above left, from Canada's Natural Resources department in Ottowa) shows the locations of landslides due to Leda clay deposited when the Champlain Sea retreated to its present size, and the blue area on the map shows the maximum extent to which the Champlain Sea previously extended into Eastern Canada.
Part of the explanation underlying the different character of quick clay (Leda clay) in this area of Canada, referred to as marine clay, is the presence of salt (from sea water) that provides sea-salt ions of NaCl acting as an adhesive between the clay particles.
If only the salt were present, the marine clay formed by this process would be quite stable, as it is elsewhere in the world.
The illustration (left, from Canada Natural Resources), shows the "anatomy of a Leda Clay landslide".
But following the retreat of the last glaciers in this area (roughly 10,000 years ago) rainwater in this area (possibly very low in mineral content), perhaps combined with a high silt content of the clay that allowed rainwater to penetrate to the clay layer, resulted in an un-stable clay soil chemistry. -- Wikipedia
Wikipedia adds that "These landslides are progressive, meaning they usually start at a river, and progress upwards at slow walking speed. They have been known to penetrate kilometers inland, and consume everything in their path."
It is not difficult to understand that a soil relying on water's surface tension can easily become unstable in response to even the smallest shock or by a larger one such as an earthquake, even a distant one. The disturbed clay changes form to a watery gel, losing its previously (and false) stable soil characteristic.
Sinkhole Repair Services
Watch out: Readers trying to diagnose and deal with sudden soil subsidence or yard collapses should
see SINKHOLES - IMMEDIATE SAFETY ACTIONS.
Companies identify themselves as sinkhole damage repair experts in Floria are listed
at SINKHOLE DAMAGE REPAIRS or select a topic from the closely-related articles below, or see the
complete ARTICLE INDEX.
Reader Question: changes in the stability of quick clay
(Oct 30, 2012) Felipe said:
Why are quickclays in quebec more unstable now than when they formed?
Reply:
Changes in water content are probably a factor. See Larson (2002) and Smalley (1976) cited below. Other researches are evaluating effects of climate change on quick clay stability.
Research on quick clay formations & Stability
- Bishop, Alan Wilfred, and Laurits Bjerrum. "The relevance of the triaxial test to the solution of stability problems." Norwegian Geotechnical Institute Publ (1900).
- Bjerrum, Laurits, and Arvid Landva. "Direct simple-shear tests on a Norwegian quick clay." Geotechnique 16, no. 1 (1966): 1-20.
- Grimstad, Gustav, and Hans Petter Jostad. "Stability analyses of quick clay using FEM and an anisotropic strain softening model with internal length scale." Nord. Geotech. Meet., Copenhagen 2 (2012): 675-680.
- Kalsnes, Bjørn, Vidar Gjelsvik, Hans Petter Jostad, Suzanne Lacasse, and Farrokh Nadim. "Risk Assessment for Quick Clay Slides–The Norwegian Practice." In Landslides in Sensitive Clays, pp. 355-367. Springer Netherlands, 2014.
- Larsen, Jan Otto. "Some aspects of physical weather related slope processes." (2002).
- Smalley, Ian. "Factors relating to the landslide process in Canadian quickclays." Earth surface processes 1, no. 2 (1976): 163-172.
- Tremblay, Marius, Karin Lundström, Victoria Svahn, Charlotte Cederbom, and Göta älv Working Group. "Inventory of landslide risk to limit consequences of climate change." In Landslide Science and Practice, pp. 403-407. Springer Berlin Heidelberg, 2013.
...
Continue reading at SINKHOLES in NEW YORK or select a topic from the closely-related articles below, or see the complete ARTICLE INDEX.
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Recommended Articles
- SEPTIC & CESSPOOL SAFETY
- SINKHOLES & SUBSIDENCES - home
- SINKING BUILDINGS
- SOIL PROPERTIES & BUILDING FAILURES
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Citations & References
In addition to any citations in the article above, a full list is available on request.
- "A Hole in the Ground Erupts, to Estonia's Delight", New York Times, 9 December 2008 p. 10.
- History of water usage in Estonia: (5.7 MB PDF) jaagupi.parnu.ee/freshwater/doc/the_history_of_water_usage_systems_in_estonia.pdf
- Kochanov, W. E., 1999, Sinkholes in Pennsylvania: Pennsylvania
Geological Survey, 4th ser., Educational Series 11, 33 p., 3rd printing April 2005, Pennsylvania Department of Conservation and Natural Resources / Bureau of Topographic and Geologic Survey, DCNR Educational Series 11, Pennsylvania Geological Survey, Fourth Series, Harrisburg,
1999 - web search 06/05/2010, original source: http://www.dcnr.state.pa.us/topogeo/hazards/es11.pdf - Quoting from the document introduction:
The first 18 pages of this booklet contain an explanation of how sinkholes develop. In order to tell the sinkhole story, it is important to discuss a number of related geologic disciplines. The words used to describe sinkholes and these disciplines may be a bit unfamiliar. However, general explanations are given throughout the booklet to help clarify their meanings.
Key words are printed in bold type for emphasis. The more important ones are defined in a Glossary that begins on page 29. The remaining sections, starting with “Sinkholes in the Urban Environment” (page 18), deal with sinkholes and their impact on our environment. This includes recognition of subsidence features and sinkhole repair. - "Quebec Family Dies as Home Vanishes Into Crater, in Reminder of Hidden Menace", Ian Austen, New York Times, 13 May 2010 p. A8. See http://www.nytimes.com/
- "Quick Clay", Wikipedia search 5/13/2010 - http://en.wikipedia.org/wiki/Quick_clay
- Foundation Engineering Problems and Hazards in Karst Terranes, James P. Reger, Maryland Geological Survey, web search 06/05/2010, original source: http://www.mgs.md.gov/esic/fs/fs11.html
Maryland Geological Survey, 2300 St. Paul Street, Baltimore, MD 21218 - "Frost Heaving Forces in Leda Clay", Penner, E., Division of Building Research, National Research Council of Canada, Canadian Geotechnical Journal, NRC Research Press, 1970-2, Vol 7, No 1, PP 8-16, National Research Council of Canada, Accession number 1970-023601, Quoting from original source
The frost heaving forces developed under a 1 ft. (30.5 cm) diameter steel plate were measured in the field throughout one winter. The steel plate was fixed at the ground surface with a rock-anchored reaction frame. heave gauges and thermocouples were installed at various depths to determine the position and temperature of the active heaving zone.
The general trend was for the surface force to increase as the winter progressed. when the frost line approached the maximum depth the force was in excess of 30,000 lb (13,608 KG).
Estimates of the heaving pressure at the frost line ranged from 7 to 12 psi (0.49 to 0.84 KG/cm) square during this period. The variation of surface heaving force was closely associated with weather conditions. Warming trends resulting in a temperature increase of the frozen layer caused the forces to decline. - "Geoscape Ottowa-Gatineau Landslides", Canada Department of Natural Resources, original source http://geoscape.nrcan.gc.ca/ottawa/landslides_e.php - quoting from that source:
Leda clay slopes in the Ottawa valley are vulnerable to catastrophic landslides. More than 250 landslides, historical and ancient, large and small, have been identified within 60 km of Ottawa. Some of these landslides caused deaths, injuries, and property damage, and their impact extended far beyond the site of the original failure. In spectacular flowslides, the sediment underlying large areas of flat land adjacent to unstable slopes liquefies.
The debris may flow up to several kilometres, damming rivers and causing flooding, siltation, and water-quality problems or damaging infrastructure. Geologists and geotechnical engineers can identify potential landslide areas, and appropriate land-use zoning and protective engineering works can reduce the risk to property and people.Deposits of Leda clay, a potentially unstable material, underlie extensive areas of the Ottawa-Gatineau region. Leda clay is composed of clay- and silt-sized particles of bedrock that were finely ground by glaciers and washed into the Champlain Sea. As the particles settled through the salty water, they were attracted to one another and formed loose clusters that fell to the seafloor.
The resulting sediment had a loose but strong framework that was capable of retaining a large amount of water. Following the retreat of the sea, the salts that originally contributed to the bonding of the particles were slowly removed (leached) by fresh water filtering through the ground. If sufficiently disturbed, the leached Leda clay, a weak but water-rich sediment, may liquefy and become a 'quick clay'.
Trigger disturbances include river erosion, increases in pore-water pressure (especially during periods of high rainfall or rapid snowmelt), earthquakes, and human activities such as excavation and construction.After an initial failure removes the stiffer, weathered crust, the sensitive clay liquefies and collapses, flowing away from the scar. Failures continue in a domino-like fashion, rapidly eating back into the flat land lying behind the failed slope. The flowing mud may raft intact pieces of the stiffer surface material for great distances.
- "Quick clay - A case study of chemical perspective in Southwest Sweden",
Yvonne Andersson-Skölda, J. Kenneth Torranceb, Bo Linda, Karin Odéna, Rodney L. Stevensc and Karin Rankkaa, Engineering Geology,
Volume 82, Issue 2, 12 December 2005, Pages 107-118
- Quoting the article abstract:
Quick clay, a soil that changes from normal firm ground to a liquid mass when it is disturbed, has been involved in most of the large and serious clay slides in Sweden, Norway and Canada. The location, time of occurrence and size of quick clay slides are difficult to predict and large slides may cause great devastation.
Some geochemical studies of Swedish quick clay were done in the 1960s and early 1970s, but no systematic studies of the interrelationships of pore water chemistry, mineralogy, geotechnical properties and other parameters on quick clays in Sweden have been published.
Such studies are of national and general interest because of the many combinations of rock flour source areas and sedimentation conditions that occurred across central Sweden and into the Baltic Sea area during deglaciation.In this study, geotechnical properties related to the in situ chemistry at one quick clay site were extensively studied, and spot sampling was conducted at two other locations in Southwest Sweden. In this area the clay minerals mainly are non-expanding phyllosilicate minerals (illite) and primary minerals (quartz, feldspar), which is consistent with previous studies of quick clay mineralogy.
Extensive leaching has occurred at all three locations. At the extensively studied site, Surte, the lowest salinity was found at the greatest depth, inferring that the leaching by fresh water was accomplished by water movement upward and laterally through the sediment from the underlying bedrock.
This is consistent with the local setting where bedrock hills rise sharply to over 100 m above the marine sediment surface. An artesian pressure would also be anticipated at this location.There is a correlation (negative) between sensitivity and salinity but there is an indication that the maximum salinity or electrical conductivity consistent with the quick clay behaviour is higher than reported elsewhere. However, for high sensitivities the salinity is about the same as reported elsewhere. In the deepest part of the borehole, there is a higher content of Fe and Al in the pore water, indicating reduced state.
Further work is needed to confirm the difference in salinity and to investigate the possible interplay of salinity and potential dispersing agents such as the role of anoxic conditions, in this region. F
urther work is especially needed in the locations where the sediment accumulation occurred under lower salinity conditions. At all three locations, high remoulded shear strength and low sensitivity have been seen near the surface together with a decrease in pore water cation concentrations. - Wikimedia Commons (Surte Sweden quick clay landslide photo described as Svenska: 1950 drabbades Surte av ett stort jordskred. En man beskådar sitt förstörda hus. Photo credit (1950, free use of images from before 1 January 1969) http://commons.wikimedia.org/wiki/File:Landslide_in_Sweden_%28Surte%29_1950,_2.jpg, Original source, http://www.gp.se/gp/jsp/Crosslink.jsp?d=518&a=501870&img=7
- [1] Sarah Cervone, [web page] data from the APIRSdatabase, Graphics by Ann Murray, Sara Reinhart and Vic Ramey, Vic Ramey is the editor. DEP review by Jeff Schardt and Judy Ludlow. The web page is a collaboration of the Center for Aquatic and Invasive Plants, University of Florida, and the Bureau of Invasive Plant Management, Florida Department of Environmental Protection contact: varamey@nersp.nerdc.ufl.edu [A primary resource for this article
- [2] Center for Cave and Karst Studies or the Kentucky Climate Center, both at Western Kentucky University
- Our recommended books about building & mechanical systems design, inspection, problem diagnosis, and repair, and about indoor environment and IAQ testing, diagnosis, and cleanup are at the InspectAPedia Bookstore. Also see our Book Reviews - InspectAPedia.
- Avongard foundation crack progress chart for structural crack monitoring
- Defects and Deterioration in Buildings: A Practical Guide to the Science and Technology of Material Failure, Barry Richardson, Spon Press; 2d Ed (2001), ISBN-10: 041925210X, ISBN-13: 978-0419252108. Quoting:
- Guide to Domestic Building Surveys, Jack Bower, Butterworth Architecture, London, 1988, ISBN 0-408-50000 X
- "Avoiding Foundation Failures," Robert Marshall, Journal of Light Construction, July, 1996 (Highly recommend this article-DF)
- "A Foundation for Unstable Soils," Harris Hyman, P.E., Journal of Light Construction, May 1995
- "Inspecting Block Foundations," Donald V. Cohen, P.E., ASHI Reporter, December 1998. This article in turn cites the Fine Homebuilding article noted below.
- "When Block Foundations go Bad," Fine Homebuilding, June/July 1998
- [1] Sarah Cervone, [web page] data from the APIRS database, Graphics by Ann Murray, Sara Reinhart and Vic Ramey, Vic Ramey is the editor. DEP review by Jeff Schardt and Judy Ludlow. The web page is a collaboration of the Center for Aquatic and Invasive Plants, University of Florida, and the Bureau of Invasive Plant Management, Florida Department of Environmental Protection contact: varamey@nersp.nerdc.ufl.edu [A primary resource for this article
- Vanity Fair - web search 06/04/2010 http://www.vanityfair.com/online/daily/2010/06/what-caused-the-guatemala-sinkhole-and-why-is-it-so-round.html
- Wikipedia - web search 06/04/2010 - http://en.wikipedia.org/wiki/Guatemala_City
- Sinclair, W. C., 1982, Sinkhole development resulting from ground-water withdrawal in the Tampa Area, Florida: U.S. Geological Survey Water-Resources Investigations 81-50, 19 p.
- White, W. B., 1988, Geomorphology and Hydrology of Karst Terrains: Oxford University Press, New York, 464 p.
- Barry F. Beck, A. J. (1999). Hydrogeology and Engineering Geology of Sinkholes and Karst. Rotterdam, Netherlands: A. A. Balkema.
- Beck, B. F. (2003). Sinkholes and the Engineering and Environmental Impacts of Karst. Huntsville, Alabama: The American Society of Civil Engineers.
- Beck, B. F. (2005). Sinkholes and the Engineering and Envrionmental Impacts of Karst. San Antonio, Texas: The American Society of Civil Engineers.
- Tony Waltham, F. B. (2005). Sinkholes and Subsidence, Karst and Cavernous Rocks in Engineering and Construction. Chichester, United Kingdom: Praxis Publishing.
- Whitman D., G. T. (1999). Spatial Interrelationships Between Lake Elevations, Water Tables, and Sinkhole Occurence in Central Florida: A GIS Approach. Photogrammetric Engineering and Remote Sensing , 1169-1178.
- Cited References from this article:
- #3. Detecting Sinkholes with Geophysics, Enviroscan, Inc., Lancaster PA 717-396-8922 email@enviroscan.com www.enviroscan.com 2003
- In addition to citations & references found in this article, see the research citations given at the end of the related articles found at our suggested
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