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

Outline Background Mechanism of Liquefaction Calculation of Liquefaction Remedial Measures Simulation

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

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.

Look Closer

Liquefaction phenomenon

Mechanism of Liquefaction

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

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

Grain Size Distribution

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

use of threshold strain If ɣ thus computed for any depth in cohesionless deposit is less than the threshold strain (typically 0.0001 or 0.01 percent), then there is safety against liquefaction.

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

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

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

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

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.

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.

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

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

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.

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

Remedial Methods Dynamic Compaction Vibrocompaction

Remedial Methods Preloading ,Vertical Drainage , Wick Drain

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

Simulation

Thank you very much for your attention!!