the coefficient of secondary consolidation, C(Section 2.3.3). The general
equation for
2 , applied to embankment and foundation in turn, is given by
2 Czlog(t 2 /t 1 ) (2.33)wherezis the height Hor depth Dfas appropriate, and times t 2 andt 1 are
determined relative to the completion of primary consolidation.
Values for Care generally below 0.002 for overconsolidated clay
fills etc., rising to between 0.005 and 0.5 for softer normally consolidated
clays.
Anticipated maximum settlements within an earthfill embankment at
end of construction for H13 m can initially be approximated from the
relationship(^) ec0.035(H 13) (m). (2.34)
2.8.2 Deformation
The internal deformations which develop are complex and are not pre-
cisely determinate. The average transverse base strain can be approxim-
ated if it is assumed that on completion of foundation settlement the base
deforms to a circular arc. For moderate settlements the average positive,
i.e. tensile, base strain (^) his then given by
(^) h 2 1 (2.35)
whereLis the base width of the embankment.
The corresponding mean vertical strain, (^) v, is expressed by
(^) v (^) e/Hmve H/2. (2.36)
Further aspects of internal deformation, notably at the critical
core–filter–shoulder interfaces, are addressed in Mitchell (1983).
2.8.3 Performance indices for earthfill cores
Progressive deterioration or inadequate performance of an earthfill core
may be indicated by excessive and possibly turbid seepage and leakage.
Other indicators include localized crest or upstream face depressions,
excessive general settlement or a high phreatic surface in the downstream
shoulder.
[(L/2)^2 ( (^) f)^2 ]1/2
L