Soil Liquefaction – Causes, Effects, And Solution?

What Is Soil Liquefaction?

Soil liquefaction is a process in which saturated or partially saturated soil loses its strength and stiffness under the application of earthquake load or sudden rapid loading conditions.

Concept Of Soil Liquefaction

In normal conditions, soil particles are connected to each other due to contact forces and provide strength to the soil.

In the saturated condition, soil pores are filled with water and get separated from each other. Soil particles are separated because soil particles exert pressure on each other.

Soil particles exert pressure due to water pressure. Water pressure increases due to earthquake loading or some other rapid loading conditions.

Importance Of Soil Liquefaction

Natural hazards such as Earthquakes cause huge disturbances on the earth’s surface and below the earth’s surface. When seismic events occur saturated soil loses its strength which can damage the structural stability and could turn fatal. Liquefaction causes an unexpected development shift that is out of sync with the remainder of the construction.

A high-intensity earthquake might cause several structural damages to the property leading to casualties. When soil is saturated it generates a quicksand effect. Due to soil liquefication building foundation can slide or overturn.

A retaining wall is constructed in the building if the building is near to water bodies like rivers, ocean, etc. A retaining wall is a structural member which is heavily dependent on the strength and stiffness of the soil. In case of soil gets liquefied, the retaining wall collapses which could cause landslides.

Types Of Soil Liquefaction

1. Flow Liquefaction:

During an earthquake, the soil particles get rearranged and cause the soil to flow like a liquid.

2. Lateral Spreading:

The soil moves laterally or horizontally, usually perpendicular to the earthquake waves.

3. Soil Liquefaction due to Cyclic Loading:

The soil experiences repeated cycles of loading and unloading, which causes the soil particles to rearrange and lose their strength.

4. Residual Liquefaction:

Soil that was previously liquefied during an earthquake remains in a partially liquefied state and can liquefy again during subsequent earthquakes.

5. Combination Liquefaction:

This occurs when two or more types of liquefaction occur at the same time.

Classification

1. Cyclic Liquefaction

Cyclic liquefaction is a phenomenon that arises due to the repeated loading and unloading of soil, which may be caused by natural calamities such as earthquakes. During this process, the water pressure in the soil rises, which results in a loss of strength of the soil, causing it to behave like a liquid.

2. Monotonic Liquefaction

On the other hand, monotonic liquefaction occurs when there is a sudden increase in the load on the soil, which may also be caused by earthquakes or landslides. This sudden increase in load causes a rapid rise in water pressure within the soil, leading to a loss of soil strength and subsequent liquid-like behavior.

Causes Of Soil Liquefaction

1. Types of soil:

The kind of soil is really important for soil liquefaction. Soft, not pressed-down soil with lots of water, like sand and silt, is more likely to turn into a liquid than hard soil like clay.

2. Water in the soil:

Water in the soil is also really important. When the soil has lots of water, it’s more likely to turn into a liquid than when it’s drier. This happens because the water makes the soil slippery and it can’t hold together as well.

3. How big the earthquake is:

How big the earthquake is makes a big difference in how likely it is that soil liquefaction will happen. When there’s a really big earthquake, the ground shakes a lot harder and can cause more soil to turn into a liquid.

4. How the ground moves:

The way the ground moves, like how fast and how long it shakes, can also make soil more likely to turn into a liquid. When the ground shakes really fast and for a long time, it’s more likely to make soil turn into a liquid than when it shakes slowly and for a short time.

Effects Of Soil Liquefaction

1. Sudden damage to the structure
2. Structure becomes unserviceable
3. Damage of utility lines
4. Structure can tilt
5. Septic tank and manholes can float in saturated soil

How To Avoid Soil Liquefaction

1. By improving drainage characteristics.
2. By increasing the density and strength of the soil.
3. Foundation design in such a way that can resist liquefication.
4. By avoiding soil that can be liquified.
   

Sum Up

Soil liquefaction poses a significant risk to structures constructed on loose or poorly compacted soils with high water content in earthquake-prone regions, causing severe damage to buildings and infrastructure, as well as injury or death to people in affected areas. Mitigation strategies, such as improving the soil, designing foundations, and retrofitting for seismic activity, can help to reduce the risk and severity of soil liquefaction. Early warning systems and public education can also play a crucial role in mitigating the effects of soil liquefaction. However, more research is necessary to better comprehend the causes and effects of soil liquefaction and to develop more effective mitigation strategies.

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