Cohesion (geology)

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Cohesion is the component of shear strength of a rock or soil that is independent of interparticle friction.

In soils, true cohesion is caused by following:

  1. Electrostatic forces in stiff overconsolidated clays (which may be lost through weathering)
  2. Cementing by Fe2O3, CaCO3, NaCl, etc.

There can also be apparent cohesion. This is caused by:

  1. Negative capillary pressure (which is lost upon wetting)
  2. Pore pressure response during undrained loading (which is lost through time)
  3. Root cohesion (which may be lost through logging or fire of the contributing plants, or through solution)

Some typical values of soil cohesion for different soils can be found on Geotechdata.info database.

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