According to Rankine's formula the minimum depth of foundation

 1. According to Rankine's formula, the minimum depth of foundation is :

p/w (1-sin Φ /1+sin Φ) 2 

where p=gross bearing capacity w =density of soil Φ =angle of the response of soil 3. But in practice, the foundation depth is kept at 0.90m or even more.

2. In case of foundation on sandy soil maximum permissible differential settlement is:

25mm

3. In case of foundation on clayey soil maximum permissible differential settlement is:

40mm