Understanding Soil Liquefaction: Causes and Effects
May 06, 2024
Category: Uncategorized
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When an earthquake occurs, soil liquefaction can occur, wherein saturated soil temporarily loses its strength and behaves like a liquid. As a result, the soil cannot withstand any load. This phenomenon can have serious consequences for infrastructure and human life. It can occur in partially saturated or saturated soils.
This phenomenon was first described by Allen Hazen in 1918 after the failure of the Calaveras Dam in California
Causes of Soil Liquefaction
An important factor in soil liquefaction is the increased pore water pressure in saturated soils. Under normal conditions, the soil particles are packed and the load is distributed among these particles. But in a saturated soil, the void is filled with water, and there is no air. When an earthquake occurs, external pressure is applied, and water in voids develops pore-water pressure.
Pore-water pressure and soil particles share the externally applied load. In some cases, the pore pressure is so high that the external force is uniformly distributed between the pore fluid and the soil particles, in which case the effective pressure is reduced to zero.
Earthquakes shake the ground and disturb the compact soil. Excess pore-water pressure is generated by the sudden application of load (or vibration), which increases the voids in soil particles. The soil loses its strength and the stiffness of the soil reduces to zero. It behaves like liquid. The soil loses its ability to support the structures built on it, and the consequences can be devastating.
Effects of Soil Liquefaction
Soil Liquefaction has catastrophic effects, such as destabilising structures as buildings and bridges, causing them to overturn, sink, or collapse, endangering lives and even damaging subsurface infrastructure such as water and drainage drains.
It also leads to secondary hazards such as landslides and tsunamis. Erosion causes failures in coastal areas can cause sudden large landslides, potentially triggering tsunamis
Below is a table summarising some of the most severe earthquakes where liquefaction occurred and the impacts of liquefaction:
| Earthquake | Location | Year | Effects of Liquefaction |
| Niigata Earthquake | Niigata, Japan | 1964 | Widespread liquefaction destroyed many buildings |
| Alaska Earthquake | Alaska, USA | 1964 | Neighbourhoods were destroyed, roads and railroads were disrupted, and more than 250 bridges were compressed or buckled |
| Loma Prieta Earthquake | San Francisco, USA | 1989 | Liquefaction caused significant subsidence, fracture, and horizontal sliding of the ground surface in the Marina district. |
| Christchurch Earthquakes | Christchurch, New Zealand | 2010-2011 | About 15,000 homes and many commercial buildings had to be demolished after liquefaction damaged them beyond repair. |
Conclusion
Soil liquefaction is a serious threat to our built environment, especially in earthquake prone areas. Understanding the underlying causes is important for adopting effective mitigation strategies. By implementing prevention strategies and improving engineering practices, we can reduce the risks associated with liquefaction and build more resilient communities.
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FAQs
Q1. Which types of soil are likely to undergo liquefaction?
A: Sandy soils are more prone to liquefaction than clayey soils. This is because, in comparison to fine-grained soils, sandy soils have more voids and little to no cohesion.
Q2. What are the different types of Soil Liquefaction?
A: The different types of soil liquefaction include flow liquefaction, lateral spreading, soil liquefaction due to cyclic loading and residual liquefaction.
Q3. What can be done to prevent soil liquefaction?
A: Understanding the causes of soil liquefaction is crucial to mitigate its damaging consequences. By identifying the causes, one can take smart steps to curb its negative effects.
