What is Pre Consolidation Pressure? Explain emperical method for determination of Pre Consolidation Pressure.

Preconsolidation pressure is the mean effective vertical stress that has acted in the clay many times in its history. From pressure void curve, Cassagrande has proposed an empirical method for the estimation of preconsolidation pressure. The procedure is described as below:

 Visually determine the point P that has the maximum curvature. Draw a horizontal line PQ. Draw Tangent `PR` at `P`. Draw the line `PS` bisecting the angle `QPR`. Produce the straight line portion of the `e-log(sigma)` plot . Plot backward to intersect `PS` at `T`. The effective pressure corresponding to point `T` is the preconsolidation pressure `sigma_(max)`.

Preconsolidation pressure is the mean effective vertical stress that has acted in the clay many times in its history. From pressure void curve, Cassagrande has proposed an empirical method for the estimation of preconsolidation pressure. The procedure is described as below:

 Visually determine the point P that has the maximum curvature. Draw a horizontal line PQ. Draw Tangent `PR` at `P`. Draw the line `PS` bisecting the angle `QPR`. Produce the straight line portion of the `e-log(sigma)` plot . Plot backward to intersect `PS` at `T`. The effective pressure corresponding to point `T` is the preconsolidation pressure `sigma_(max)`.

Fig: Graphical procedure for the determination of preconsolidation pressure