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1. General Guidelines for Depth
Minimum Depth: Shallow footings are typically placed at a depth of 12 to 24 inches below the ground surface. This ensures stability and prevents surface disturbances (e.g., erosion, vegetation) from affecting the footing.
2. Frost Depth: In regions with freezing temperatures, footings must be placed below the frost line to prevent frost heave. However, in the Araucanía Region of Chile, frost depth is not a significant concern due to the mild climate.
3. Soil Bearing Capacity: The footing must be deep enough to reach a soil layer with adequate bearing capacity. In the Araucanía Region, volcanic soils (Andisols) may require deeper footings if the surface soil is weak or expansive.
4. Seismic Considerations: In seismic zones, footings are often placed deeper to improve stability and reduce the risk of settlement during earthquakes. The lateral bracing can be seen in these wooden piles to ensure seismic activities there.
Use spread footings for light to moderate loads on stable soils.
I think the best bid for this project without further working drawings. A cut line should be placed in between the footings at least 4′ to avoid a conclusion of depth of the foundations.Always consult a geotechnical engineer and structural engineer to ensure the footing depth is appropriate for the site conditions and structural requirements.By following these guidelines, you can determine the appropriate depth for a shallow spread footing in the Araucanía Region or similar areas, but we are NOT certain the soil condition is adequate or not. I hope this helps you make important decisions in regard to the foundation of this project. Please see the attached document in regard to Araucania’s foundation design.