Quick clay

Quick clay, also known as Leda clay and Champlain Sea clay in Canada, is any of unique sensitive glaciomarine clays found in Canada, Norway, Russia, Sweden, Finland, the United States and other locations around the world. The clay is so unstable that when a mass of quick clay is subjected to sufficient stress, the material behavior may transition from that of a particulate material to that of a fluid.

Quick clay has a remolded strength and so is much less than its strength upon initial loading. That is caused by a highly unstable clay particle structure.

Quick clay is typically originally deposited in a marine environment. In that environment, the positive charge of cations (such as sodium) was able to bind clay particles (negative surface charge) by balancing charge in the double layer. When the clay became uplifted and was no longer subjected to salt water conditions, rainwater infiltrated these clays and washed away the salts that allowed these clay particles to remain in a stable structure.

With shear stress, the lack of counterbalancing charge from salts in the quick clay results in clay particle repulsion and realignment of clay particles to a structure that is extremely weak and unstable. Quick clay regains strength rapidly, however, when salt is added, which allows clay particles to form complexes with one another.

Quick clay is found only in northern countries, such as Russia, Canada, Norway, Sweden, and Finland, and in Alaska, United States since they were glaciated during the . In Canada, the clay is associated primarily with the Pleistocene-era Champlain Sea, in the modern Ottawa Valley, the St. Lawrence Valley, and the Saguenay River regions.

Quick clay has been the underlying cause of many deadly landslides. In Canada alone, it has been associated with more than 250 mapped landslides. Some of these are ancient, and may have been triggered by earthquakes.

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