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[mohdshaikvali786@gmail.co]

Dear engineers


I have received a Raft foundation design at ground floor level for a G+2 floor precast building for review. Raft footing thickness 700mm at main PC 260mm wall at periphery of the building and remaining part is 250mm thick raft for supporting partition PC wall 100mm thick.SBC of sandy soil is 170kn/m^2.Is there any codal provision for the minimum depth for Raft foundation?Please give me your valuable advice and feedback for review of  the design Raft at ground level.
find attached raft section.




Thank You. Regards
Shaik Vali.

SEFI
Member

[vikram.jeet]

Foundation depth :-

It shall be minimum, I think, 500mm below NGL provided sbc
has been worked accordingly. But generally foundation depth is 0.9 to 1.5 m bgl depending on soil strata.

In yr case  foundation depth = 700 mm raft + 80mm pcc levelling conc = 780mm which is ok from NBC, but sbc needs to be available at this level.

In case good soil is not there at this Found level of 780mm , then either make pcc 1:5:10 fill from firm strata level to this level Or lay raft at firm strata and inside fill sand upto Plunth level less flooring layers.

Pl see National building Code of India  , chapter on foundations,, or IS code on design and construction of raft foundation.

[mohdshaikvali786@gmail.co]

Thank you for valuable advice 🙏