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[Er.Ajith_K]

Greetings!

I like to know how to calculate the elastic settlement of a shallow foundation in sand. I'm not able to the get the answer. I will provide the necessary details below:

Soil type: Coarse Grained Type
Soil : Medium Dense Sand
Avg N: 11
All bearing capacity : 130 kPa
Footing Type: Isolated Column Footing
Design footing width: 1.5m
Depth of the foundation below ground level: 2.2m
Effective depth of foundation below ground level: 1.7m

As per IS 1904, permissible limits for isolated column footing is 50mm. Actual answer I should get is 48mm but I'm not getting it. Can someone please help me in solving this ?

With Regards

Ajith

[Zia]

Hi Ajith,

It will be better if you post your calculation.

From the information provided it is very hard to find out why your calculated value is not 48mm.

Based on elastic theory, settlement at the corner of a footing = net pressure x width x ((1-Poisson's Ratio^2)/Modulus of Elasticity) x Influence Factor(s).

Generally influence factors are applied to settlement formulas based on elastic method. These factors are based on depth of influence, footing depth etc. So your estimated settlement value (which is less than or greater than 48mm) will depend on the type of factors you have used in your calculation.

Please see Bowles book "Foundation Analysis and Design" for details.

Regards,
Zia