1. An- Najah National University Faculty of Engineering Civil Engineering Department
“LIQUEFACTION”
Prepared By: Husni M. Awwad
Talal Z. Zammar
Supervisor: Dr. Isam Jardaneh

2. Outline Background Mechanism of Liquefaction
Calculation of Liquefaction
Remedial Measures
Simulation

3. History Introduced by Arthur Casagrande (1935-8)
Serious attention because of Japan, Alaska and Nigata earthquake in 1964.
Evidence of liquefaction found in prior earthquakes

4. Review Liquefaction Definition: σ’=σt-u
The amplified movement of the ground, occurring after earthquake when the ground becomes over saturated with water and transforms from solid to a liquid state due to increase in pore water pressure and reduction in effective stress.

5. Look Closer

6. Liquefaction phenomenon

7. Mechanism of Liquefaction

8. Types of Failure Overturning Sand Boiling Subsidence and Settlement
Cyclic Mobility
Overturning
Sand Boiling
Subsidence and Settlement
Deferential Transient Motion

9. Calculation of Liquefaction
There are three major methods :
Grain size distribution
Threshold strain
CSR & CRR

10. Grain Size Distribution

11. Threshold Strain Equation: Can be write in this formula :
ɣ= 1.2 a z/ v2s

12. use of threshold strain
If ɣ thus computed for any depth in cohesionless deposit is less than the threshold strain (typically or 0.01 percent), then there is safety against liquefaction.

13. Cyclic Stress Ratio (CSR) and Cyclic Resistance Ratio (CRR)
Calculation or estimation of two variables is required for evaluation of liquefaction resistance of soils (CSR), (CRR)
CSR = (τav/σ'vo) = 0.65 (amax/g)(σvo/σ'vo)rd

14. Method for Evaluating CRR
Cone penetration test (CPT)
Standard penetration test (SPT)
Shear-wave velocity measurements (Vs )
Becker penetration test (BPT)

15. Standard Penetration Test (SPT)
(N1)60 = NmCNCECBCRCS
Correlations for Fines Content and Soil Plasticity

16. Cone Penetration Test (CPT)
procedure are on average slightly smaller, and thus more conservative.

17. Shear Wave Velocity The advantages of using VS :
VS can be accurately measured in situ using a number of techniques .
VS measurements are possible in soils that are difficult to penetrate with CPT and SPT.
measurements can be performed in small laboratory specimens.
VS is directly related to small-strain shear modulus.

18. Becker Penetration Tests (BPT)
CPT and SPT measurements, however, are not generally reliable in gravelly soils. Large gravel particles may interfere with the normal deformation of soil materials around the penetrometer increasing penetration resistance.

19. Magnitude Scaling Factors
FS = (CRR7.5/CSR)MSF

20. Remedial Methods Deep Soil Mixing Compaction Grouting
Dynamic Compaction
Vibrocompaction
Vertical Drains “Wick Drain”
Stone Columns

21. Remedial Methods Advantages : Reduce foundation settlement.
Increase shear strength to improve slope stability.
Increase bearing capacity
Increase water permeability to accelerate drainage and thereby accelerate foundation settlement.
Prevent soil liquefaction during earthquakes.

22. Remedial Methods Deep Soil Mixing 1- Dry soil mixing
2- Wet soil mixing
Compaction Grouting

23. Remedial Methods
Dynamic Compaction
Vibrocompaction

24. Remedial Methods
Preloading ,Vertical Drainage , Wick Drain

25. Remedial Methods Stone Column ,Vibro-Replacement 1- Wet (top feed)
2- Dry (bottom feed)

26. Simulation

27. Thank you very much for your attention!!