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Bearing Capacity – Criteria
To design a stable foundation, stability is dependent on a value of bearing capacity.
Soil bearing capacity designed for the minimum value of following.
Perform independent investigation because of independent criteria.
So let us learn about Bearing Capacity – Criteria and factors affecting.
- Shear failure of foundation or Bearing Capacity failure:-
– Bearing capacity failure happens because of the Plastic flow of soil material and lateral expansion of soil.
PLASTIC FLOW IS THE STATE IN WHICH THE BODY CONTINUES TO DEFORM UNDER CONSTANT APPLIED FLOW.
– By providing the soil with adequate bearing capacity, we can avoid failure.
– This is the Shear Strength criteria.
- Probable settlement:-
– The expected settlement should be within permissible limits so to avoid damage to the stability of the structure.
– This is the Settlement criteria.
In the previous post, we discussed the terms related to Bearing capacity, here we discussed the basis for bearing capacity which will play the important role during design.
Now let us see what are the factors which will affect the bearing capacity
Factors affecting bearing capacity of the soil.
Following are the factors which affect the bearing capacity of the soil.
- Nature of soil and its property.
- Nature of foundation and other details like its size, shape, depth below ground level, and rigidity of ground surface.
- Total and differential settlement that structure can withstand without failure.
- Location of the groundwater table.
- Initial stresses in soil (if any).
1. Nature of soil and its property
Dense soil will have more bearing capacity as compared to loose soil because the unit weight of dense soil is more than loose soil.
2. Shape of Foundation
Even if the soil is soft below the foundation, Raft/Mat foundation will perform better as it spreads the load in a wider area.
3. Amount of settlement
if the settlement is more than allowable settlement, the bearing capacity will be lower.
4. Location of the groundwater table.
If the water table is above the foundation, then the submerged weight of water is considered and overburden pressure is calculated. It is observed that in such cases, the bearing capacity reduces to around 50%.
5. Initial stresses in soil (if any).