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| 3. |
Bearing capacity of square and circular footings
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If the soil support of a continuous footing yields due to the imposed loads on the footings, all the soil particles move parallel to the plane which is perpendicular to the centre line of the footing. Therefore the problem of computing the bearing capacity of such footing is a plane strain deformation problem. On the other hand if the soil support of the square and circular footing yields, the soil particles move in radial and not in parallel planes. Terzaghi has proposed certain shape factors to take care of the effect of the shape on the bearing capacity. The equation can be written as,
where,
 are the shape factors whose values for the square and circular footings are as follows,
For long footings: 
For square footings: 
For circular footings: 
For rectangular footing of length L and width B :  =  , 
Skempton has given the values of N c for purely cohesive soils, as given below:
For ( Df / B) < 2.5, |
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( Nc) for rectangular footing =  |
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( Nc) for circular and rectangular footing =  |
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For ( Df / B) >= 2.5, |
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( Nc) for rectangular footing =  |
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Then,
Where,
C u is the undrained cohesion of the soil. |
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