Live and dead loads surcharge for tieback block retaining walls

[mdt7]

For the design of segmental block (tieback) retaining walls, specifically for the Rockwood Classic 8 wall system, are there typical design values for live load and dead load surcharge that are generally used for site projects? For example, I have seen several examples that seem to use 100 psf for a parking lot surcharge, and 250 psf for a building surcharge. If there are accepted design values, where can I find them? Thanks.

 

[PEinc]

Surcharge loads on a block geogrid wall are no different than surcharges on other types of walls. Building surcharge loads (vertical) can be approximately 10 to 30 times greater than 250 psf. You need to know more about the adjacent buildings, including wall and column loads and how far away and how deep the buildings' foundations are.

In highway design, the minimum traffic surcharge per AASHTO is equal to 2 feet of dirt surcharge or 250 psf (vertical) minimum. Can trucks (e.g., moving trucks, fire trucks, delivery trucks, etc.) get to the back of the proposed wall?

 

[mdt7]

I am familiar with the AASHTO traffic surcharge (2 x gamma x h). I am assuming that I can use this for cases when I have heavy traffic loads directly behind the wall. The Design Manual for Segmental Retaining Walls by NCMA says that common live surcharge magnitudes for pavement loading are 100 psf for car and light truck traffic, and 250 psf for tractor trailer traffic, fire lanes, or highway loading.

Am I correct in assuming that these surcharge loads should be considered if the loads are applied inside the soil failure plane? For example, in the case of a slab foundation, should I apply the portion of the slab that is transmitting the load inside the failure plane?

 

[PEinc]

If you have a footing load and a slab load, you should apply both. If you are using a computer design program, they usually allow more than one surcharge to be applied. Locate the loads where they are. The program will add in the appropriate portion of surcharge(s) for each trial failure surface.

 

[mdt7]

The program I'm using is called SRWall, which is based on the Segmental Wall Design Manual. It has only two inputs for surcharge: a field for live load surcharge, and a field for dead load surcharge. There is no way to input the location of the loads. The program seems to apply these loads from a point immediately behind the wall out to infinity (or at least past the failure surface). I am guessing this is a conservative analysis?