What Is Foundation?
A foundation is the element of a structure which connects it to the ground and transfers loads from the structure to the ground. Foundation engineering is the application of soil mechanics and rock mechanics (Geotechnical engineering) in the design of foundation elements of structures.
Types of Foundation
Following are different types of Foundations used in construction:
Shallow Foundation
Following are different types of Shallow Foundations used in construction:
- Individual Footing
- Combined Footing
- Strip Foundation
- Raft or Mat Foundation
- Spread Footing Foundations,
- Slab-On-Grade Foundations,
- Pad Foundations,
- Rubble Trench Foundations
- Earthbag Foundations
Deep Foundation
Following are different types of Deep Foundations used in construction:
- Pile Foundations
- Caissons Foundations
- Cylinders Foundations
- Basements Foundations
- Hollow Box Foundations (Buoyancy Rafts)
- Shaft Foundations
Shallow Foundation Definition
A shallow foundation is a type of building a foundation that transfers building loads to the earth very near to the surface, rather than to a subsurface layer or a range of depths as does a deep foundation. Shallow foundations include spread footing foundations, mat-slab foundations, slab-on-grade foundations, pad foundations, rubble trench foundations and earthbag foundations.
Shallow foundations are constructed where soil layer at shallow depth is able to support the structural loads. The depth of shallow foundation is generally less than its width.
It can be used where the bearing capacity of soil on which the structure is to be constructed is maximum then Shallow Foundation can be used. Minimum depth of this Foundation is 800mm and maximum depth not to be taken more than 4 meters.
Deep Foundation Definition
A deep foundation is a type of foundation that transfers building loads to the earth farther down from the surface than a shallow foundation does to a subsurface layer or a range of depths. A deep foundation is required to carry loads from a structure through weak compressible soils or fills on to stronger and less compressible soils or rocks at depth, or for functional reasons.
Deep foundations are founded too deeply below the finished ground surface for their base bearing capacity to be affected by surface conditions, this is usually at depths >3 m below finished ground level.
How Deep Are Foundations?
The words shallow and deep refer to the depth of soil in which the foundation is made. Shallow foundations can be made in depths of as little as 3ft (1m), while deep foundations can be made at depths of 60 – 200ft (20 – 65m).
Difference Between Shallow and Deep Foundation
| Sr. No. | Detail | Shallow Foundation | Deep Foundation |
| 1 | Meaning | Shallow means having little depth. | Deep means extending far away from a point of reference, especially downwards. Extending far down from the top or surface |
| 2 | Definition | Foundation which is placed near the surface of the earth or transfers the loads at shallow depth is called the shallow foundation. | Foundation which is placed at a greater depth or transfers the loads to deep strata is called the deep foundation. |
| 3 | Cost | A shallow foundation is cheaper. | Deep foundations are generally more expensive than shallow foundations. |
| 4 | Types of Foundations | Shallow foundations include strip footing, isolated footings, combined footings, mat foundations, and grade beams. | Deep foundations include pile caps, piles, drilled piers, and caissons. |
| 5 | Depth of the Foundation | Shallow foundations can be made in depths of as little as 3ft (1m) | Deep foundations can be made at depths of 60 – 200ft (20 – 65m). |
| 6 | Shape of Footing | A shallow foundation is a rectangular or square shape. | A deep foundation is a bit circular and cylindrical shape. |
| 7 | Feasibility | Shallow foundations are easier to construct. | A deep foundation is more complex. |
| 8 | Mechanism of Load Transfer | Shallow foundations transfer loads mostly by end bearing. | Deep foundations rely both on end bearing and skin friction, with few exceptions like end-bearing pile. |
| 9 | Advantages | Construction materials are available, less labour is needed, construction procedure is simple at an affordable cost, etc. | Deep foundation can be provided at a greater depth, Provide lateral support and resist uplift, effective when foundation at shallow depth is not possible, can carry a huge load, etc. |
| 10 | Disadvantages | Possibility of a settlement, usually applicable for lightweight structure, weak against lateral loads, etc. | More expensive needs skilled labours, complex construction procedures, can be time-consuming and some types of deep foundations are not very flexible, etc. |
FAQs About Foundations in Construction
What is a foundation in construction?
A foundation is a structural element that connects a building to the ground and transfers loads from the structure to the underlying soil or rock.
What are the main types of foundations used in construction?
Foundations are broadly categorized into shallow foundations and deep foundations. Shallow foundations include spread footing, mat-slab, slab-on-grade, pad, rubble trench, and earthbag foundations. Deep foundations include pile, caisson, cylinder, basement, hollow box, and shaft foundations.
What is the difference between shallow and deep foundations?
Shallow foundations are placed near the surface of the earth and transfer loads at shallow depths, typically less than 3 meters. Deep foundations, on the other hand, are placed at greater depths, often beyond 3 meters, to transfer loads to deeper, more stable soil or rock strata.
How do you determine whether to use a shallow or deep foundation?
The choice between shallow and deep foundations depends on factors such as soil conditions, the size and type of structure, loading requirements, and economic considerations. Shallow foundations are preferred where the soil can support the loads at shallow depths economically, while deep foundations are used when surface soil conditions are unsuitable or when high loads need to be transferred to deeper, more competent soil or rock.
What are the advantages of shallow foundations?
Shallow foundations are generally more cost-effective, easier and quicker to construct, require less excavation, and are suitable for structures with lighter loads and stable soil conditions near the surface.
What are the advantages of deep foundations?
Deep foundations are effective for transferring heavy loads to deeper, more stable soil or rock, provide resistance against lateral forces and uplift, and can be used in areas with weak or compressible surface soil.
What are some common applications of shallow foundations?
Shallow foundations are commonly used for residential buildings, smaller commercial structures, and structures with relatively light loads and stable soil conditions near the surface.
When are deep foundations typically used?
Deep foundations are used when the soil near the surface is unable to support the loads imposed by the structure, when structures require resistance against lateral forces or uplift, or when economic considerations favor deeper foundations over extensive excavation or soil improvement.
What factors affect the choice of foundation type in construction?
Factors such as soil type and bearing capacity, structural loads and design requirements, groundwater conditions, site constraints, environmental considerations, and project budget and schedule influence the selection of foundation type in construction.
How can foundations be designed to minimize settlement and ensure stability?
Foundations are designed based on geotechnical investigations to assess soil conditions and bearing capacity. Techniques such as proper footing design, reinforcement, soil improvement, and drainage systems are used to minimize settlement and ensure the long-term stability of structures.
