Secondary consolidation of soft soils

The conventional method to compute secondary consolidation of soft soils does not reflect the influence of load.It is only applicable to the normally consolidated soils actually.However,we often deal with overconsolidated soil in engineering problems.The tests performed by the authors show that secondary compression obviously relates to load on the overconsolidated soil.In this paper,the concept of absolute and relative time coordinate systems is proposed,and it is suggested to use the absolute time coordinate system in computation of secondary compression.In absolute time coordinate system, the beginning of loading on normally consolidated soil is taken as the origin of time.Based on Bjerrum’s theory of equitime e-lgp curve and the absolute time coordinate system,a new method to compute secondary compression is developed.Through the equitime e-lgp curve,the relationship between time and load is set up.Then the secondary compression varies not only with time,but also with load.It can be used for both normally consolidated soil and overconsolidated soil.The proposed model of secondary consolidation can explain many tested phenomenon and engineering problems,such as influences of preloading and repeat of loading and unloading on secondary consolidation.