Coulomb Earth Pressure Theory - Angle of Sloping Backfill 1

[LearningAlways]

Hello All.

I am a structural engineer who works for a precast company. Our retaining walls retains soil that slopes down and away from our precast walls. We design garages and typically use precast walls to retain soil for our ramps where we transition from slab-on-grade to our precast double tees. We typically and conservatively design as if our retaining is flat but my question is could we use a negative angle for Beta in Coulomb's equation. Can it be that simple to use a negative angle for Beta to find the soil pressures on our wall? Please and thank you for your help.

 

[geomane]

They have some charts in NAVFAC DM 7.1 for the conditions you are describing.

 

[ukbridge]

There are also some (rather convoluted) equations in Eurocode 7 you can use, or alternatively you can use a program like FREW to get the earth pressures out.

 

[SlideRuleEra]

Our retaining walls retains soil that slopes down and away from our precast walls.

What is the slope of the ramps and how high are the walls? Rather than trying to derive a general solution, that info will help come up with a reasonable approximation... which is what Coulomb's (and Rankine's) equations are anyway.

http://www.SlideRuleEra.net

http://www.VacuumTubeEra.net

 

[PEinc]

The answer is YES. However, if there is a chance in the future that someone will level off the soil behind the wall, you may be better using beta = 0 degrees.

http://www.PeirceEngineering.com

 

[fattdad]

the answer is yes, but. . .

You are likely going to have a wall that can't rotate. The charts are likely to address active or passive earth pressure, but. . .

If the wall cannot rotate to engage the active earth pressure, you'll need to obtain at-rest earth pressures. In my practice, I've just taken to getting the active earth pressure and multiplying it by 1.5. That's at-rest enough for me!

f-d

ípapß gordo ainÆt no madre flaca!

 

[PEinc]

LearningAlways, a sketch would have been helpful.

http://www.PeirceEngineering.com

 

[LearningAlways]

Please see sketch attached.

 

[LearningAlways]

Maybe...

 

[LearningAlways]

PEinc: We won't likely ever see that ramp taken down or altered. Anyone who would be altering the ramp would be deconstructing the garage so we possibly could use the negative angle.

 

[PEinc]

Thanks. That downward slope is so flat that I would ignore it.

http://www.PeirceEngineering.com

 

[MTNClimber]

I agree with PEinc. That's not much of a slope. I don't know why but I was assuming something much steeper.

 

[fattdad]

in light of the drawing, the juice isn't worth the squeeze.

f-d

ípapß gordo ainÆt no madre flaca!