Seven Factors that Can Impact the Bearing Capacity of Soil

A lot of factors influence the soil’s bearing capacity. These include strength, the depth and width of the foundation, foundation spacing, as well as soil weight and surcharge. Aside from these factors, non-load-related factors must also be taken into account when designing foundation and computing the capacité portante des sols. These factors include frost action, repeated movement, possible heave, soil reinforcement, soil erosion, and others. Bearing capacity refers to the soil’s ability to handle the pressure it is subjected to when a structure is built on it. Keep reading to learn more about how these factors influence soil bearing capacity:

The Strength of the Soil

Mixed soil and cohesionless soil have an unproportioned increased bearing capacity as the effective friction angle increases. But, cohesive soil can have a linear bearing capacity with the soil cohesion as long as there is zero effective friction angle.

The Depth and Width of the Foundation

A greater bearing capacity means a deeper foundation. But, bearing capacity is reduced when the foundation is brought down to a weak layer of soil. To ensure adequate bearing capacity, foundations must be placed at depths where there is an equal weight between the structure and the displaced soil.

Meanwhile, the width of the foundation impacts the cohesionless oil’s bearing capacity. Cohesive soil that has infinite depth and constant shear strength has bearing capacity that depends on the width of the foundation.

Cyclic Movements

Repeated or cyclic movements could increase the foundation soil’s pore pressure, reducing its bearing capacity. They come from vibrating machinery, earthquakes, pile driving, blasting, and others. A reduction in pore pressure can lead to the liquefaction of the foundation soil. This results in decreased effective stress to zero, causing structures to settle and lose bearing capacity.

Foundation Spacing

When designing the foundation, the minimum spacing between footings must be taken into consideration. This ensures bearing capacity is not reduced.

Frost Action

In some soils, frost heave can change bearing capacity when it comes into contact with water and is subjected to freezing temperatures. Frost action is common in low cohesion materials that contain significant silt-sized particles.

Collapsible and Expansive Soils

These soils can possess significant strength and bearing capacity if dry. But, their volume can change because of water content changes, resulting in foundation movements. Because of seasonal wetting and drying cycles, soil movements will occur, resulting in excessive long-term structure deterioration.

Subsurface Voids

Subsurface voids are located deep beneath the foundation. They can change the soil’s bearing capacity.