Modular Block Retaining Wall

[DebbieDell]

I am being asked by the township engineer to add surcharge on a retaining wall next to a residential driveway. I have been looking through manuals, but do not see any standard. What is required as a minimum surcharge load? I already designed it to handle 120 PCF isn't that enough and what regulations do I follow? Help!!!

 

[BurgoEng]

see this thread...

http://www.eng-tips.com/viewthread.cfm?qid=138859

I am working on something similar and am just going to go with 250psf at the surface to play it safe.

It seems to me it's all judgement with retaining walls. Quite dishearting if you ask me. These are the things they never teach you in school and then you have to just work your way through in the real world, without any real directions.

 

[oldestguy]

DOT members can help on this, but why 120 pcf?

Back it down to at rest or active, depending on what your backfll is and give yourself some breathing room.

 

[dik]

There are a couple of products out that have software that designs the walls and produce drawings (reasonably good). A couple that I'm aware of are Allen Block and Risi...

For residential I often use 50 psf superimposed load (design of parkades is for 50 psf). The software includes the effect... sort of treated as an extra foot of soil or whatever. For commercial work I often use 100 psf just to accommodate effects of heavier equipment. If you have a garbage truck parking near the top of the wall you may have difficulties. I assume by the 120 pcf that you are dealing with a granular backfill and using some component of this for active earth pressure?

Dik

 

[DebbieDell]

I am using the risiwall program and already submitted the calculations to the town with 120 psf and he is asking for more than that. Is that nec? It is a residential driveway.

 

[Panars]

AASHTO standard is two feet of earth which is at least 240 psf. Some people bump this up to 250 psf.

 

[dik]

You should be able to input the soil characteristics and you will not likely have 120 psf... unless you have swelling clays or something of that ilk... likely more like 60 psf hydrostatic for clays or maybe 40 psf for gravels.

The 120 should be capable of providing for the surcharge...

Try running the program with soil types... Allen Block program also allows use of soil parameters...

Dik

 

[BurgoEng]

IS there a quick way to use the Allan Block program (ABwall) that doesn't require you to input the full wall profile, plan, several sections, etc....? Something similar to the Keystone Wall program that allows you to just input one section cut with a height and soil props and adjust the geogrid props? I'd like to be able to use the AB program, for quick and dirty calcs/estimates but there is so much input required (unless I haven't explored it enough) that makes it counter productive to use.

 

[DebbieDell]

I have had several times in which I called AB support and I do know you can skip the plan section. They told me it is best to skip it if you have a CAD drawing already for the plan view. The other sections I believe you need to go through. There support team is great and worth a call if you have spec. questions.

 

[dik]

I haven't used the feature, but there is a mathcad template that comes with ABWall... might be for a quick solution...

Dik

 

[MSEMan]

AASHTO requires 100 pcf for lightly trafficked areas etc. This should be more than adequate. 250 psf for highways.

Are you designing to LRFD or ASD method?

 

[ctbailey]

ABWalls 2000 (The Allan Block Program) does allow you to jump directly to "section design." No need to enter any "elevation view" or "plan view" or even the "panel view."

If you do go through the LABOROUS process of cranking through the elevation and plan views, the output drawings and specs are actually very nice.

But, they included "SECTION 0" in the sections design that is intended to be used for quickie jobs.

I called tech support, and they scheduled a phone call with me. They called me on the specified day, and we worked through a tutorial for about an hour.

Ever since then, I can actually utilize the program. I have even used the cutom block to analyze non-allan block MSE walls.

Craig

___
Craig T. Bailey, PE

http://www.bailey-associates.com