SEMINAR ON LIQUEFACTION

INDEX

1. INTRODUCTION                                                                                4

2. LIQUEFACTION                                                                                 5

3. OCCURRENCE OF LIQUEFACTION                                               8

4. MECHANISM OF LIQUEFACTION                                                12

5. EVALUATION OF LIQUEFACTION POTENTIAL                       19

6. FACTORS AFFECTING LIQUEFACTION                                     20

7. HAZARDS DUE TO LIQUEFACTION                                            21

8. PREVENTION OF LIQUEFACTION                                               24

9. CONCLUSIONS                                                                                 25

10. REFERENCES                                                                                    26

3

LIQUEFACTION

INTRODUCTION

Liquefaction is a phenomenon in which the strength and stiffness of a soil is

reduced by earthquake shaking or other rapid loading. Liquefaction and related

phenomena have been responsible for tremendous amounts of damage in historical

earthquakes around the world.

Soil liquefaction describes the behavior of soils that, when loaded, suddenly go

from a solid state to a liquefied state, or having the consistency of a heavy liquid.

Liquefaction is more likely to occur in loose to moderate saturated granular soils with

poor drainage, such as silty sands or sands and gravels capped or containing seams of

      Liquefaction occurs in saturated soils, that is, soils in which the space between

individual particles is completely filled with water. This water exerts a pressure on the

soil particles that influences how tightly the particles themselves are pressed together.

During loading, usually cyclic undrained loading, e.g. earthquake loading, loose sands

tend to decrease in volume, which produces an increase in their pore water pressures and

consequently a decrease in shear strength, i.e. reduction in effective stress.

Deposits most susceptible to liquefaction are young (Holocene-age, deposited

within the last 10,000 years) sands and silt of similar grain size (well-sorted), in beds at

least several feet thick, and saturated with water. Such deposits are often found along

riverbeds, beaches, dunes, and areas where windblown silt (loess) and sand have

 Liquefaction has been observed in earthquakes for many years. In fact, written

records dating back hundreds and even thousands of years describe earthquake effects

that are now known to be associated with liquefaction. Nevertheless, liquefaction has

been so widespread in a number of recent earthquakes that it is often associated with

them. Some of those earthquakes are Alaska in USA (1964), Niigata in Japan (1964),

Loma Preita in USA (1989) and Kobe in Japan (1995).

Although the effects of liquefaction have been long understood, it was more

thoroughly brought to the attention of engineers and seismologists in the 1964 Niigata,

Japan and Alaska earthquakes. It was also a major factor in the destruction in San

Francisco's Marina District during the 1989 Loma Preita earthquake.

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