Consolidation of Soils

Primary compression and secondary compression of saturated soils are consistent with the Terzaghi effective stress principle. Both primary compression and secondary compression and associated settlement and increase in undrained shear strength result from the rearrangement of soil particles to more compact packing, assisted by soil particle deformation, soil particle compression, and soil particle damage. The secondary compression behavior of soils is well explained and predicted by the C_α/C_c law of compressibility. The debate on the independence of end-of-primary (EOP) void ratio versus effective vertical stress relation from the duration of primary consolidation continues in spite of the following series of convincing evidence (a) EOP e versus σ'_v relation from laboratory consolidation tests is independent of the duration of primary consolidation, (b) preconsolidation pressure mobilized in the field is equal to EOP preconsolidation pressure determined from laboratory oedometer tests on 20 mm thick undisturbed soil specimens, (c) surface and subsurface settlements measured in the field during primary consolidation of soil subjected to embankment loading are equal to the settlement predicted using the EOP e versus σ'_v relation from laboratory oedometer tests on 20 mm thick undisturbed soil specimens, and (d) data on compressibility with time, (∂e / ∂t)_σ'v, provide an explanation for the independence of EOP e versus σ'_v relation from the duration of primary consolidation. There is no direct observed evidence supporting the "extreme" hypothesis B.