Which foundation to choose for heaving soils

Heaving soils are soils that are prone to significant volume changes with changes in moisture content. These soils include:

• Clayey soils

• Loams

• Loess-like soils

The main characteristic of heaving soils is their ability to expand when wet and frozen, and to contract when dried and thawed. This phenomenon is called soil heaving and can cause serious damage to the foundation and the entire building structure.

Main problems when building on heaving soils

 

1. Foundation heave and deformation: Soil heave causes the foundation to heave and shift unevenly.

2. Cracks in walls and floors: Foundation deformations lead to cracks in walls, floors, and other building structures.

3. Reduced bearing capacity: When thawing, the soil can lose its strength, reducing the bearing capacity of the foundation.

4. Uneven Settlement: Heaving soils can settle unevenly, causing distortion and deformation of the building.

Types of Foundations for Heaving Soils

The following types of foundations are suitable for construction on heaving soils:

1. Pile Foundation. A pile foundation involves the installation of piles that transfer the building load to denser and more stable soil layers located below the heaving level.

Advantages:

• Resistance to soil heaving.

• Can be used in areas with high groundwater levels.

• Durability and reliability.

Disadvantages:

• High installation cost.

• Requires specialized equipment for pile installation.

Use screw piles or bored piles. Screw piles are easier to install and can be driven manually, while bored piles require specialized drilling equipment.

2. Strip foundation with a depth below the frost line. A strip foundation is a continuous strip of concrete laid around the perimeter of a building. When building on heaving soils, a strip foundation must be buried below the frost line.

Advantages:

• Simple design.

• Good stability when properly embedded.

Disadvantages:

• High cost due to the large amount of excavation and concrete.

• Labor-intensive installation.

Ensure the foundation depth exceeds the frost line in your region. This will prevent the foundation from heaving when the ground freezes.

3. Slab Foundation. A slab foundation is a monolithic concrete slab that evenly distributes the building load across its entire surface.

Advantages:

• High resistance to uneven soil heaving.

• Simple design and installation.

Disadvantages:

• High cost of concrete and reinforcement.

• Requires careful foundation preparation.

A slab foundation is particularly suitable for lightweight buildings and structures, such as single-story houses or outbuildings. Ensure the base beneath the slab is thoroughly prepared and compacted.

4. Foundation on a non-heaving pad. This type of foundation involves creating an artificial pad of non-heaving materials (sand, crushed stone) beneath the foundation.

Advantages:

• Reduces the impact of heaving soils on the foundation.

• Simplicity and cost-effectiveness.

Disadvantages:

• Requires careful preparation and quality control of the pad.

• Suitable only for lightweight structures.

The pad thickness must be sufficient to compensate for soil heaving. Typically, this is a layer of sand or crushed stone at least 30-50 cm thick.

Recommendations for choosing a foundation on heaving soils

1. Conducting a geological survey: Before starting construction, conduct a detailed geological survey of the soil on the site. This will help determine its composition, frost penetration level, and bearing capacity.

2. Consider climate conditions: Determine the depth of soil freezing in your region and take this into account when selecting and designing the foundation.

3. Proper foundation preparation: Regardless of the foundation type, carefully prepare the foundation. Ensure that the non-heaving material bed is well compacted and drained.

4. Use high-quality materials: Use high-quality, corrosion-resistant materials for piles and reinforcement. This will ensure the durability of the foundation in challenging conditions.

5. Professional approach: Engage experienced professionals for foundation design and installation. Improper execution can lead to serious problems in the future.