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Suitable Foundation ???

Suitable Foundation ???

Suitable Foundation ???

(OP)
I am designing a single story light gauge steel structure inside the sea on island, so soil bearing capacity is 0.4kg/cm^2 (very loose sandy soil) at a depth 1 m below the road level so my question is that which type of foundation is suitable and economical for this light gauge steel building ???
Before client was interested in RCC superstructure with the pile foundation, due to the huge price of foundation he changed his mind to light gauge steel structure.
Your valuable suggestions will highly be appreciated.

RE: Suitable Foundation ???

(OP)
any one can reply please ??

RE: Suitable Foundation ???

Where did you get the value of 0.4kg/cm2? That is extremely low.
How deep is the loose sandy soil?
What lies below it?
Do you have a soil report? If not, why not get one?

BA

RE: Suitable Foundation ???

(OP)
Thanks for your reply BAretired
i got this value after soil investigation . water is encounter after 1.8-2.0 m from NSL.
this value (0.4Kg/m^2) is taken at the level of 1m below the NSL
below is the single page screen shot of conclusion and recommendations of soil investigation report.

RE: Suitable Foundation ???

Several questions come to mind.

What is the nature of your building (its use? its sensitivity to settlement?)? Really - is the building more like a storage shed or a building to house staff etc.
How big is your building? What column loads?
What is the frost depth?
How sensitive is the seismic activity in your area?

If the structure is small, I can see that one would be looking for a way to stay away from deep foundations. Would could "densify" the sand by using dynamic compaction (dropping a heavy weight from a crane from a height). One could also consider the use of stone columns. There are times you could simply remove the upper 2 m of fill (or to your water level), and recompact. but the fact that you have loose sands to depth and the area's potential for seismic activity is unknown to us at present, I would not likely recommend this. Use of stone columns would be, likely, a good bet.

RE: Suitable Foundation ???

The question BA asked remains: where did you get the 0.4kg/cm^2 value? That is only about 40 kPa or 800 PSF, very low. The screen shot you showed us only addresses the recommended piled foundation. When you go back to the geotech for more information, you need to ask as well for settlement advice for a building founded on shallow footings.

RE: Suitable Foundation ???

(OP)
0.4 Kg/m^2 bearing capacity is the geology department recommendation for shallow foundation for this site.
this is a small public market building (Area = 784m^2 total weight of the structure is approximately 30 ton ) which will be construct in light gauge steel structure so there will be no column or point load , all loads will be UDL (uniform distributed loads) which will go through the light gauge steel walls to the foundation .
maximum settlement recommended 25 mm
building is in seismic zone 0.
i hope above information is comprehensive.

RE: Suitable Foundation ???

Based on the data available, a pile and grade beam foundation would seem to me to be the best choice.

BA

RE: Suitable Foundation ???

"so there will be no column or point load"
I'm not clear on the framing. Is it steel stud type framing? Self-framing metal wall panels like Butler used to make?

RE: Suitable Foundation ???

(OP)
@BUGGAR..Yes this is steel stud type framing.
can we go with raft foundation/slab foundation or we need to improve the soil bearing capacity ?
if we improve the soil bearing capacity by removing soft material and adding some granular material (silt+sand+gravels)then 1kg/cm^2 will be enough for raft foundation??

RE: Suitable Foundation ???

Quote (shahq123)

can we go with raft foundation/slab foundation or we need to improve the soil bearing capacity ?
if we improve the soil bearing capacity by removing soft material and adding some granular material (silt+sand+gravels)then 1kg/cm^2 will be enough for raft foundation??

These are questions which should be discussed with your geotechnical engineer. He may need to perform consolidation tests to get a better idea of the probable performance of the upper soil. You should provide him with design loading on the slab and edge loading around the perimeter of the building.

BA

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