Volume 6 – Geotechnical Manual, Site Investigation and Engineering ...

Chapter 5 INTERPRETATION OF SOIL PROPERTIES
For the case of clays and silts above the water table, the soils may have degrees of saturation
between 0 to 100%. Full saturation can occur due to capillarity effects and varies as the atmospheric
weather. The identity relationship for total unit weight is:
γ T = 1+w n
1+e o G sγ w
The estimation of unit weights for dry to partially saturated soils depends on the degree of
saturation, as defined by (5.4) and (5.5).
Figure 5.4 Interrelationship between Saturated Unit Weight and In-Place Water Content Of Geo-
Materials
The total overburden stress (σ vo ) is calculated from:
σ vo = ∑ T ∆z (5.6)
which in turn is used to obtain the effective vertical overburden stress:
σ vo ’ = σ vo - u o (5.7)
where the hydrostatic porewater pressure (u o ) is determined from the water table.
5-6 March 2009