Pricing
289/33310–15FE Reference Handbook 10.4 · Civil · Geotechnical · Secondary Compression
1. Effective Stress2. Rankine Active Earth Pressure3. Terzaghi Bearing Capacity (strip)4. Void Ratio5. Porosity and Degree of Saturation6. Moist Unit Weight7. Darcy’s Law (Seepage)8. Mohr–Coulomb Failure Criterion9. Primary Consolidation Settlement10. Atterberg Limits and Plasticity Index11. Relative Density of Sand12. Slope Factor of Safety13. Time Factor Tv and Drainage Path14. Pile Capacity: Tip and Skin15. Proctor Compaction16. Flow Net Discharge17. Rankine Passive Earth Pressure18. Retaining-Wall Sliding FS19. USCS Classification (Cu, Cc, PI)20. Coulomb Active Earth Pressure21. Immediate (Elastic) Settlement22. OCR and Preconsolidation Stress23. Infinite-Slope Factor of Safety24. Hazen Estimate of k25. Secondary Compression Cα

Handbook formula

Secondary Compression Cα

After primary consolidation (Tv≈1, t=tp), some clays creep. Cα is the slope of e vs log t in that range. Organics and highly plastic clays are the usual FE suspects.

Secondary compression index
End-of-primary time
Void ratio at end of primary

Step-by-step solved example

Cα=0.02, H=4 m, ep=1.0, t1=1 yr, t2=10 yr. Ss?

sandCαrocklog t
After primary, e vs log t with slope Cα.

  1. 1. log

    log10(10/1)=1.

  2. 2. Ss

    0.02×4/(2)×1=0.04 m=40 mm.

Answer: Ss = 40 mm

10 practice questions

0/10 correct

1.t2/t1 = 100 → log=

2.Cα/Cc is often about

3.If you start the log at tp too early you

4.Peat settlements are dominated by

5.H=8 m, Cα=0.01, 1+ep=2, one log cycle: Ss=

6.Preloading longer than tp can

7.e vs log t after tp is

8.Units of Cα are

9.Primary Sc uses Cc or Cr and

10.A 10-fold time increase at constant Cα