Cohesionless vs. Cohesive

Attribute	Cohesionless	Cohesive
Definition	Particles are not bonded together	Particles are bonded together
Strength	Lower strength	Higher strength
Internal friction	Lower internal friction	Higher internal friction
Shear strength	Lower shear strength	Higher shear strength

Cohesionless

Cohesionless materials are those that do not have any internal strength or cohesion. They rely on external forces to hold them together. Examples of cohesionless materials include sand, gravel, and dry soil. These materials have a tendency to flow or shift easily when subjected to external forces, such as water flow or vibrations.

One of the key attributes of cohesionless materials is their lack of internal friction. This means that particles within the material do not stick together, making it easier for the material to move or shift. Cohesionless materials are often used in construction for applications where drainage or permeability is important, such as in road construction or as backfill material.

Another attribute of cohesionless materials is their ability to undergo significant volume changes without losing their strength. This makes them ideal for use in applications where settlement or consolidation is expected, such as in embankments or foundations.

Cohesionless materials are also known for their ability to withstand high loads without undergoing significant deformation. This makes them suitable for use in applications where stability under heavy loads is crucial, such as in retaining walls or bridge abutments.

In summary, cohesionless materials are characterized by their lack of internal strength, high permeability, ability to undergo volume changes, and resistance to deformation under high loads.

Cohesive

Cohesive materials, on the other hand, are those that have internal strength or cohesion. This means that the particles within the material stick together, providing the material with stability and resistance to deformation. Examples of cohesive materials include clay, silt, and wet soil. These materials have a tendency to stick together and form a solid mass when subjected to external forces.

One of the key attributes of cohesive materials is their high internal friction. This allows the particles within the material to stick together, making it difficult for the material to flow or shift. Cohesive materials are often used in construction for applications where stability and strength are important, such as in building foundations or retaining walls.

Another attribute of cohesive materials is their low permeability. This means that water or other fluids have difficulty passing through the material, making it ideal for applications where water retention or containment is necessary, such as in dams or levees.

Cohesive materials are also known for their ability to maintain their shape and strength under low to moderate loads. This makes them suitable for use in applications where stability under normal conditions is crucial, such as in building footings or road subgrades.

In summary, cohesive materials are characterized by their internal strength, low permeability, ability to maintain shape under moderate loads, and resistance to deformation.

Comparison

When comparing cohesionless and cohesive materials, it is important to consider their key attributes and how they impact their performance in different applications. Cohesionless materials are known for their lack of internal strength, high permeability, ability to undergo volume changes, and resistance to deformation under high loads. On the other hand, cohesive materials have internal strength, low permeability, ability to maintain shape under moderate loads, and resistance to deformation.

• Cohesionless materials rely on external forces to hold them together, while cohesive materials have internal strength.
• Cohesionless materials are highly permeable, while cohesive materials have low permeability.
• Cohesionless materials can undergo significant volume changes without losing strength, while cohesive materials maintain their shape under moderate loads.
• Cohesionless materials are resistant to deformation under high loads, while cohesive materials are known for their stability under normal conditions.

Overall, the choice between cohesionless and cohesive materials depends on the specific requirements of the application. Cohesionless materials are often preferred for applications where drainage, permeability, and resistance to high loads are important, while cohesive materials are suitable for applications where stability, low permeability, and resistance to moderate loads are crucial.