Soil Foundation
- Footings are generally the lowermost supporting part of the structure known as sub-structure and are the last structural elements through which load is transferred to foundation comprising soil/rock.
- Structural elements transfer the applied loads from one part of the building to the other. These are in turn transmitted to the foundation which transfers it to the underlying soil/rock.
There are generally two types of Foundation in Civil Engineering:-
1. Shallow Foundation
2. Deep Foundation
2. Deep Foundation
| Shallow Foundation | Deep Foundation |
|---|---|
| According to Terzaghi, the Width of the foundation is greater than the Depth of the foundation. | According to Terzaghi, the Depth of the foundation is greater than the Width of the foundation |
| According to Skempton's, Depth is less than equal to 2.5 times the width of the foundation | According to Skempton's, Depth is greater than 2.5 times the width of the foundation |
| Isolated Footing | Pile Foundation |
| Combined Footing | Pier Foundation |
| Raft Footing | Well/Caisson |
| Strip Footing | 15.0 |
Shape and size of Foundation depends on:-
1. Load.
2. Position of the water table.
3. Purpose of Foundation.
4. Bearing capacity of the soil.
Guidelines to adopt Foundation-
1. Load is very low, the soil is medium to dense- Shallow Foundation.
2. Load is heavy - Raft Foundation.
3. Cohesive soil(Up-heaving occur) - Under-Reamed Pile.
4. Running water - Well/Caisson.
5. Loose sand - Pile Foundation.
IS Code guideline for Safety
1. Single/Double Footing- Depth at least 30 cm.
2. Multistorey Structure - Depth 60 cm.
3. Snow area - Depth of footing from ground level is below the frost action.
4. Depth of footing from ground level is below the organic layer(Root of Tree).
5. In the slopping area depth is greater equal to 90cm and edge distance is greater equal to 60cm.
2. Deep Foundation
3. Soil Exploration
4. Expansive Soils