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

Chapter 4 SOIL SETTLEMENT
Figure 4.5 Typical Consolidation Curve for Under-Consolidated Soil
4.4 RATE OF CONSOLIDATION
The average degree of consolidation, U at any time, t, can be defined as:
U = S t / S ult (4.7)
Where S t = Settlement at time of interest
S ult = Settlement at end of primary consolidation (i.e. at ultimate) when excess pore water
pressures are zero throughout the consolidating layer
Figure 4.6 shows the average degree of consolidation (U) corresponding to a normalized time
expressed in terms of a time factor, T v , where :
T v = c vt
H d
2
(4.8)
which can be written
t T v H d
2
C v
(4.9)
2
c v
= coefficient of consolidation (m /day)
H d
= The longest distance to a drainage boundary (m)
t = time (day)
March 2009 4-7