Design of subgrade for factory slab

[Balageotech]

Dear Experts,

Pl. advice the approach to estimate settlement and subgrade reaction (theoretically) for Factory slab(grade slab) having live load of 70 kN/m2. Allowable settlement is 0.

I have the existing soil of clay having N value 15 that extents for 20.0m.

Liquid limit is 60 and Plasticity index is 30, but water table not encounter till 30.0m below. Di I need to consider the expansivity of clay?

Thanks in Advance.

Regards
Bala

 

[oldestguy]

Chances are your soil has a significant potential for expansion and/or shrinkage, depending on moisture content changes. That N value would indicate a near stable condition, but moisture content and unconfined compression value as well as laboratory consolidation tests would tell more. Knowing the pre-consolidation pressure from these tests would help to answer a question about potential for settlement.

Asking for zero settlement is asking a lot, since there is likely "some" settlement, but probably not noticeable.

For this material any moisture changes will have resulting either lifting or lowering of the floor. Thus, any trees nearby should be removed and no fast growing trees should be planted within 50 meters. Site drainage also must prevent adding of water.

 

[L0k]

Hi Bala, the differential settlement for raft between corner and the center of the slab will be about 1 by 4.
However, if you need the allowable zero settlement you should install piles.