The types of structural foundation and their use cases

Geotechnical foundations are an essential part of structures included in much of the built environment of our world today. Buildings, bridges, and other infrastructure projects are all built on foundation. But what are the main categories of foundation we use?

The main pourpose of foundations is to transfer the loads from the structure above into the underlying soil or rock in a safe and stable manner. Here is a quick-fire list of the most common types of foundation we use:

1. Shallow Foundations:

   • Spread Footings: These are wide, flat pads that distribute the load over a larger area. They are commonly used for individual columns or walls.
   • Mat Foundations: Also known as raft foundations, they cover a larger area and support multiple columns or walls. They are used for structures with heavy loads or on weak or expansive soils.

2. Deep Foundations:

   • Piles: These are long, slender structural elements driven into the ground or formed in situ. They transfer loads through skin friction and/or end-bearing. Piles are suitable for deep or weak soil conditions.
   • Drilled Shafts: Also known as drilled piers or caissons, they are large-diameter, deep excavations that are reinforced with steel and filled with concrete. Drilled shafts are used for structures with heavy vertical loads or in areas with high lateral loads.
   • Micropiles: These are small-diameter piles, often less than 300mm, typically installed using drilling techniques. Micropiles are used in restricted access areas or for retrofitting existing structures.
   • Sheet Piles: These are interlocking steel or concrete sheets driven into the ground to create a barrier against soil or water. Sheet piles are commonly used for retaining walls, cofferdams, or bulkheads.

3. Earth Retaining Structures:

   • Retaining Walls: These structures are used to retain soil and prevent erosion or landslides. They can be made of various materials such as concrete, stone, or gabions.
   • Soil Nailing: It involves reinforcing the soil with steel bars or other materials to improve stability. Soil nailing is often used for excavations or slopes.
   • Anchored Walls: These walls are supported by tensioned anchors that are embedded into the ground. They are used to stabilize tall or inclined structures.

Each type of geotechnical foundation has specific design considerations and selection of the correct foundation type and geometry should be based upon soil conditions, load requirements, and construction constraints. Geotechnical engineers analyze the site conditions and undertake a soil investigation to gather the information needed for their design before the detailed design of any foundation takes place.

Have you tried our free foundation design calculator? Try it out here