properties of engineered fill 2

[monopoly]

Hi,
may be a dump question since I am structural engineer not pavement or geotech, but I have to check the bearing capacity and settlement of the structures on the compacted engineered fill. My question is what is the difference between the well graded gravel bearing capacity, i.e. 80mm minus pit-run gravel, 40mm minus gravel, 20mm minus gravel etc. Where I can get the properties (bearing and elastic modulus ) for this type of compacted granualar fill.

 

[cvg]

typically, you would want to obtain these values and calculations from your geotech.

 

[msucog]

it's a function of several things so rely on the experience of a "qualified" geotechnical engineer

 

[oldestguy]

Hi:

That Geotech may find that you have more to worry about with the soil below that compacted granular layer. Give that person all the scoop on loads and desired foundation type.

 

[msucog]

and don't forget to discuss the expected performance of the structure (i.e. maximum tolerable differential/total settlement the structure can withstand...the geotech can approximate whether the foundation soils might/might not cooperate)

 

[fattdad]

Just to add to the discussion.

Bearing capacity is usually determined on the basis of foundation performance. As a geotechnical engineer there may be some soil strength that would support a very heavily-loaded footing before failure. However, there may be too much settlement associated with that soil strength, either in the form of elastic compression or consolidation. As such, the geotechnical engineer usually recommends an allowable bearing pressure based on settlement (typically controlled to 1 in or less).

Now, let's consider a 200 kip column footing designed for 3,000 psf. You may have the bearing grade of the column 2 ft below the floor slab elevation and it would be about 8 ft square. For a footing that's 8 ft square, you must consider the relavance of soils that extend to depths of 12 to 16 ft - not just whether there is some 2 ft thick subbase of this aggregate or that aggregate.

Now let's consider a "typical" soil profile. You're likely to have multiple layers of soil in the 12 to 16 ft that underlie the foundation. Each of these layers may have different bahavior. The role of the geotechnical engineer is to characterize these engineering properties and develop a set of recommendations that limits risk to the structural performance.

That's my job in a nutshell.

Hope this helps.

f-d

¡papá gordo ain’t no madre flaca!

 

[Mickney]

To piggy-back on fatdad, the amount (or depth) of new fill placed to reach final grades is also very important and critical to settlement calculations. There is big difference in estimating foundation settlement for a site where 4 feet of fill is to be placed to reach final grade versus a site where 40 feet of fill is to be placed to reach final grade.