Pore Pressure Dissipation Vs Depth

The rate of transfer of pore pressure to effective stress is a function of depth. In other words, in the boundaries which are near to drainage path pore pressure dissipates more quickly, while for the further areas it takes longer. In this figure different patterns of pore pressure dissipation are illustrated for a soil layer which is drained at its  upper and lower surfaces.

Regarding to these curves, equation below is derived at any given depth. The important point is that at the end of consolidation, additional pore pressure is equal to zero, and not the amount of pore pressure. At the end of consolidation, the increase of soil effective stress is equal to additional pore pressure at the beginning of consolidation.