WHAT IS SOIL LIQUEFACTION - CAUSES AND EFFECTS

Soil Liquefaction

Soil liquefaction is a phenomenon in which saturated or partially saturated soil substantially loses strength and stiffness in response to an applied stress such as shaking during earthquake.Soil liquefaction occurs in a fully saturated soil.

Causes Of Liquefaction

The soil is a mixture of soil particles that are connected together.These particles are naturally rest upon each other due to gravity.Soil liquefaction occurs due to sudden and rapid load on the soil particles.The sudden water pressure leads to soil losing its cohesive strength.Once the soil loses its cohesion, it gets softened, weak and loses its solid properties that are converted to liquid properties.

Effects Of Liquefaction

1. Sand Boiling
2. Surface Landslides
3. Damage To Offshore Structures
4. Failure Of Dams And Retaining Walls
5. Failure Of Structure Under Earthquake

1. Sand Boiling

When liquefaction occurs below the surface that is fully compacted, the water pressure below the surface makes the water to break out like a bubble.These come out as boiling water.This is called as sand boiling.

2. Surface Landslides

The term landslide describe a wide variety of processes that result in the downward and outward movement of slope-forming materials including rock, soil, artificial fill or a combination of these.The failure of water carrying bodies can result in surface landslides.

3. Damage To Offshore Structure

Liquefaction is common in soil that is submerged.These conditions cause huge damage for the bridge construction, structures supporting submerged soil deposit.

4. Failure Of Dam And Retaining Wall.

The soils supporting Dams and Retaining walls undergoes liquefaction which results in the collapse of these structures.

5. Failure Of Structure Under Earthquake

Liquefaction takes place when loosely packed, water-logged sediments at or near the ground surface lose their strength in response to strong ground shaking.They can either split or lean bringing complete collapse of the structure.Past earthquake records have shown a huge failure of building structures due to liquefaction.When these types of hazards take place it can't provide enough time to evacuation, thus it result in a huge loss of life and property.

Method Of Reducing Soil Liquefaction Hazards

1. By Avoiding Liquefaction Susceptible Soils
2. Built Liquefaction Resistant Structures
3. Improve The Soil

1. By Avoiding Liquefaction Susceptible Soils

Avoid construction on liquefaction susceptible soils.There are various criteria to determine the liquefaction susceptibility of a soil.By characterizing the soil at a particular building site according to these criteria one can decide if the site is susceptible to liquefaction.

2. Built Liquefaction Resistant Structures

If it is necessary to construct on liquefaction susceptible soil because of space restrictions, favorable location, or other reasons, it may be possible to make the structure liquefaction resistant by designing the foundation elements to resist the effects of liquefaction.

3. Improve The Soil

Improving the soil involves mitigation of the liquefaction hazards by improving the strength, density and drainage characteristics of the soil.This can be done using a variety of soil improvement techniques.