According to IS specifications in any case depth of foundation in sand and clay should not be less than _________ respectively.

Explanation:

As per Cl. 7.2, IS:1904,

All foundations shall extend to a depth of at least 50 cm below the natural ground level.

The minimum depth of footing on sandy soil is 0.8 - 1 m, for rocky soil, it is 0.05 - 0.5 m and for clayey soil, it is 0.9 - 1.6 m.

The minimum depth of foundation for the load-bearing wall is 900 mm.

Important Points

The design of building foundations is performed based on prescribed serviceability and strength criteria laid down by various standard codes adopted by different countries.

Generally, the total settlement of a foundation is described under the serviceability criterion; whereas a strength criterion is described by bearing capacity of the soil or rock underlying the foundation.

As per Rankine formula, minimum depth of foundation is given as

\({{\rm{D}}_{\rm{f}}} = \frac{{\rm{q}}}{{\rm{\gamma }}} \times {\left( {\frac{{1 - {\rm{sin}}\phi }}{{1 + {\rm{sin}}\phi }}} \right)^2}\)

Where,