Dear Ashkan, 

You can check the next links.

1. http://www.sciencedirect.com/science/article/pii/S026772611200259X

2. http://www.nees-cityblock.org/archive/docs/Mech-of-seism-ind-settlement_2010.pdf

3. http://publications.eng.cam.ac.uk/603885/

4. http://publications.eng.cam.ac.uk/345874/

5. http://publications.eng.cam.ac.uk/342394/

I hope it helps.

Hi dear Ashkan 

The traditional method proposed by Buisman (1936) is practical in estimating

secondary consolidation settlement (Terzaghi et al, 1996; Poulos et al, 2002). In this method,

the magnitude of secondary consolidation is assumed to vary linearly with the logarithm of

time. It is usually expressed as :

sc = Cα 1 + eo Ho log tstp 

where sc = secondary consolidation

Cα = secondary compression index

eo = initial void ratio

Ho = thickness of soils subject to secondary consolidation

tp = time when primary consolidation completes

ts = time for which secondary consolidation is allowed

you can see your answer in these book 

Hans-Georg Kempfert

Berhane Gebreselassie

Excavations and Foundations in Soft Soils

and 

FOUNDATION DESIGN AND

CONSTRUCTION

GEOTECHNICAL ENGINEERING OFFICE

Civil Engineering and Development Department

The Government of the Hong Kong

Special Administrative Region