Foundation Settlement and Soil Compression - Elements of Soil Mechanics - page 349

Fig. 11.18 Stress paths in the consolidation test.
Fig. 11.19 Effective stress path for the general consolidation of a normally consolidated clay.
11.8.3 Stress path for general consolidation
The effective stress plot of Fig. 11.19 represents a typical case of general consolidation. The soil is normally
consolidated and point A represents the initial K 0 consolidation; AB is the effective stress path on the
application of the foundation load and BC is the effective stress path during consolidation.
Skempton and Bjerrum's assumption that lateral strain effects during consolidation can be ignored
presupposes that the strain due to the stress path BC is the same as that produced by the stress path
DE. The fact that the method proposed by Skempton and Bjerrum gives reasonable results indicates that
the effective stress path during the consolidation of soil in a typical foundation problem is indeed fairly
close to the effective stress path DE of Fig. 11.19. There are occasions when this will not be so, however,
and the stress path method of analysis can give a more reasonable prediction of settlement values (see
Lambe, 1964, 1967) . The calculation of settlement in a soft soil layer under an embankment by this pro-
cedure has been discussed by Smith ( 1968a) , and the method is also applicable to spoil heaps.