##  [Soil Liquefaction](/soil-liquefaction-0) 

 Definition

A phenomenon in which saturated, loose, unconsolidated soils abruptly lose shear strength and stiffness and behave like a fluid under transient or cyclic dynamic loading, commonly during earthquakes but also under other rapid loadings.

 

 

 

 

 

 





## Principle

Principle

Under dynamic loading, rapid increases in pore water pressure reduce effective stress; if drainage is insufficient the soil skeleton cannot sustain contact forces, causing a collapse of structure and a dramatic drop in shear resistance (flow or cyclic mobility).

 

 

 

 

 





## Demonstration

Demonstration

A layer of clean, loose saturated sand experiences repeated shear from ground shaking; pore pressures build to near overburden so that bearing capacity is lost, resulting in lateral spreading, large settlements and floatation of buried objects.

 

 

 

 

## Misapplication

Misapplication

Using 'liquefaction' loosely to describe any temporary softening, large settlement from consolidation, or non-saturated strength loss; or attributing observed ground damage solely to liquefaction without distinguishing other processes (e.g., slope instability, amplification).

 

 

 

 

 





## Consequence

Consequence

When liquefaction occurs, foundations lose bearing, retaining structures and slopes can fail, and infrastructure suffers large displacements; proper recognition drives foundation design (improvement, densification, drainage) and seismic hazard planning.

 

 

 

 

## Reversal

Reversal

Densified, cemented, coarse-grained or well-drained soils resist pore-pressure build-up and maintain contact forces, behaving as solids even under strong dynamic loading; drained cyclic loading produces different, often smaller, responses.

 

 

 

 

 





## Boundary

Boundary

Applies to saturated, cohesionless or loose granular soils (sands, silty sands) subjected to transient or cyclic shear where pore pressures can rise faster than they can dissipate; excludes cemented, coarse gravels with sufficient drainage, non-saturated soils, and long-term consolidation processes.

 

 

 

 

 





## Semantic Tension

Semantic Tension

Tension between 'liquefaction' as an instantaneous loss of shear strength and related concepts such as cyclic mobility, flow failure, or simple consolidation settlement; these processes share mechanisms but differ in conditions and outcomes.

 

 

 

 

 





## Synthesis

Synthesis

Soil liquefaction is the dynamic pore-pressure–driven loss of intergranular contact strength in saturated loose soils under rapid loading, producing fluid-like behaviour, loss of bearing capacity and potential lateral flow and settlement.