What is the minimum foundation width to be used in the bearing capacity formula

[USER10]

Hello

i have a small square pad to carry high concentrated temporary loading on a road surface. i am just approaching this as a foundation problem . i was wondering if there is any minimum requirement for foundation width (B) when using the traditional bearing capacity formula, at least theoretically .

Much appreciated

 

[EireChch]

I don’t think there is a theoretical limit, just as long as you satisfy BC and settlement. And include at least 100 mm of concrete between your column (?) and pad edge.

Give us some more detail, what’s the load and how is it transmitted to the pad?

 

[USER10]

Thanx EireChch .
Temporary surface heavy wheel load (250 kn) over s small concrete or steel pad with 0.6 m width and length. Just wanted to make sure that bearing capacity of square footing is applicable to small footings but it seems to be no problem.

 

[maxim22]

That sounds a bit like a plate load test size and force.

You don't want the area of the pad to be similar size to the soil particles resisting. But in your example it sounds like the particles below are confined by the existing road surface which will load spread. Punch failure might be a risk but I think the load is probably too low.

 

[MotorCity]

What does your Geotech report specify for minimum footing width and allowable bearing pressure?

Typically I see reports specify around 3' minimum width for a spread footing.

 

[fattdad]

define, "Small" and define, "High" then we'll have something to discuss.

f-d

ípapß gordo ainÆt no madre flaca!

 

[MTNClimber]

I believe they did. 250 kN wheel load over a small (0.6m x 0.6m) concrete or pad.

The bearing capacity formula should work for a footing of that size. That is a large load so I would expect to see some settlement and cracking in the road if you don't fail the soil.

 

[maxim22]

Maybe try a small test by jacking up heavy vehicle on a plate check for damage as you increase the load.

 

[mmarlow]

Anything under a 3' footing, I reduce the bearing capacity by the ratio B/3. Im not sure if this is written in any code, or if its just a rule of thumb my superiors use.

-MMARLOW EIT

 

[Okiryu]

I think that the IBC indicates that the minimum width for foundations is 300 mm.

But based on the size of your pad (0.6m x 0.6m), I think that a plate bearing test will give you very useful information.

Anyway, based on your load and pad size, you are putting about 700 KPa of bearing pressure. Not sure if your soils can give you that presure with an adequate FOS. Perhaps you will need to replace at least 1.2 m of soil with good engineering granular fill to get the bearing capacity that you need.

 

[geojosh84]

What is tha pad for? We need more info.