Effect of water table on Effective stress

Hi,

Effect of water table on effective stress:

Effective stress = total stress - pore water pressure.

Here we will consider the different levels of the water table with respect to the soil section where the effective stress is to be considered.

When the water table is above the section:

Consider the section A-A:
                         Effective stress = 0
Section D-D:    
                          Effective stress = Total stress - pore pressure = H1.d

Section B-B:
                          Effective stress = H1.d + H2.d1 - H2.dw   = H1.d + H2. d1'
                                         [ here d1= saturated density of soil1 and dw = water density]

Section C-C
                          Effective stress = H1.d + H2.d1 + H3.d2 - (H2+H3).dw
                                                  = H1.d + H2. d1' + H3.d2'

as d1' is always smaller than d1 it can be said that the effective stress will decrease with the rise in the water table and it will increase with the fall in the water table for any kind of soil.

Thanks!