Bearing capacity, slope stability, safe slope hiegth

[dzitse]

Please would someone help me how to estimate the bearing capacity of a foundation soil for waste dump design. It is not pure clay, but rather c and phi soil material.
I need your help
Thank you.

 

[PEinc]

Have you tried looking in any soil mechanics or foundation engineering books? I don't know how much site specific information you can get in a forum.

 

[Riggly]

You have this under Slope Stability. I assume you are not concerned just about bearing capacity but also slope stability. There are several resources on bearing pressure, all over the internet. Are you looking at a silty material? FHWA got some free publications on bearing capacity also. Concerning bearing and stability issues, you can consult NAVFAC DM 7.1 & 7.2 which you can download online for free. I would maybe simplify the soil properties for analysis, except if you have lab results of c and phi to substantiate. If the soil is more sandy than clay, I would analyze as sand, and vice versa if it is more clayey. But for slope stability you would be much better of using an acceptable computer program.

 

[fattdad]

This is one of the stupidest aspects of landfill design! It's like the regulators have no clue what "bearing capacity" means! There is no answer to this question, so you have several choices: Make one up (kind of goes against your P.E. license) or give them the real answer. The real answer is to address slope stability of the underlying soil.

The rational method for calculating "bearing pressure" is fundamentally a rotational shear failure mode. It's essentially a slope stability function, but the driving force is from a load applied on the surface. If you can show that "bearing soils" below the sloping waste can support the fill slope and maintain a safety factor of X.0 to x.5 or such, you have essentially "solved" the bearing capacity problem. Bear in mind (no pun intended) that this bearing capacity "solution" will have no relation to building foundations and that's a good thing. If you need to address bearing pressures for building foundations, you'd need to resize the problem and use the foundation width, stress bulb and things of this nature (well address settlement too).

I remain baffled that the need to solve for "bearing capacity" below landfills remains in the regulations so many years later. . .

f-d

¡papá gordo ain’t no madre flaca!

 

[BigH]

I agree that this is not a "bearing problem" but is definitely one of slope stability. It is funny, in a strange sense, in that engineers I met in India for embankments also determine the "bearing capacity" of the embankment! There is a good paper by Mike Fabius in one of the recent Canadian Geotechnical conferences on a slope failure of a garbage dump.

 

[dzitse]

Would someone help me with the Mike Fabius paper?

Why are some people not considering the issue as impact of a vertical load on underlying material which have limit to the load it can carry. What is your view.

 

[fattdad]

Why are some people not considering the issue as impact of a vertical load on underlying material which have limit to the load it can carry. What is your view.

Not sure what this means. A slope stability assessment of the waste and its interaction with the "foundation soil" (i.e., deep-seated rotational failure or wedge type failure depending on the geology) is exactly what you describe. If you consider the macro scale a waste pile mobilizes stresses to great depths and can induce shear failure (depending on soil strength) along a number of failure planes. This "impact of a vertical load on underlying material" needs to be evaluated. However, if you think about it, it's not the vertical loading that's really being evaluated, but the shearing forces that lead to the rotational failure. If you just want to evaluate the impact of vertical loading do a settlement calculation and move on. . .

f-d

¡papá gordo ain’t no madre flaca!

 

[dzitse]

fattdad

Thank you. Do you have some materials to that effect ?