Pic of the day #15 (Lithostatic Vs Hydrostaic pressure)

Graph of lithostatic versus hydrostatic pressure as a function of depth in the Earth’s crust.
A Mohr diagram showing how an increase in pore pressure moves the Mohr circle toward the origin. The increase in pore pressure decreases the mean stress (?mean), but does not change the magnitude of differential stress (?1 – ?3). In other words, the diameter of the Mohr circle remains constant, but its center moves to the left.


Pic courtesy: Earth Structure – An introduction to structural geology and toctonics


    1. Differential stress value is given by : (?1-?3)
      ?1 – ?3 > ?1 (we want this condition to be true)
      Solving the inequality we will get
      -?3 > 0
      ?3 < 0
      For (?1-?3) value to be greater than ?1, there is only one condition which is when ?3 is negative.
      We know that, ?3 will be negative in tensile domain i.e. the left hand side of the Mohr’s plot

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