Retaining Wall Surcharges

[9952bt]

I'm designing a concrete retaining wall that will act as a loading dock for a 100 kip loader. How do I convert this to a surcharge to use for design?

 

[RWF7437]

Get a few references like this one:

DEPARTMENT OF THE ARMY EM 1110-2-2502
U. S. Army Corps of Engineers
CECW-ED Washington, D. C. 20314-1000
CECW-EG
Engineer Manual 29 September 1989
No. 1110-2-2502
Engineering and Design
RETAINING AND FLOOD WALLS

Good luck

 

[SirAl]

As a follow-up to RWF7437 you can find the manual in this "must-have" link

http://www.usace.army.mil/publications/eng-manuals/cecw.htm

 

[JedClampett]

An easy way to approximate this is to calculate the footprint load of the vehicle and add it as a soil surcharge. As an example, if the footprint of the loader is 200 sq. ft. and it weighs 100 kips, the footprint load is 500 psf. If your soil weighs 125 pcf, you'll add in a 4 ft. surcharge. We use this trick extensively to simulate a H20 loading by adding a 2 ft. surcharge.

 

[9952bt]

What is an H20?

 

[BigH]

H20 - AASHTO highway loading of "typical" truck. Do a search - we have defined it in another post - or two. In India, they like to use 24kPa uniform surcharge loading for normal highway traffic. Your 100kip loading is a bit more - so likely you would use a somewhat higher surcharge but would keep the surcharge focused on a smaller area - you aren't likely to have traffic jams of the loader sitting at the same location.

 

[SirAl]

The 'surcharge equivalent' method that JedClampett points out is a clever method. For a loader though, I would be concerned with a high point loading condition, especially when the bucket is fully loaded and approaching the tipping load. This would tend to concentrate the tare of the loader + payload of the bucket onto the front axle. Perhaps using Boussinesq point load or line load would be a better way of analyzing the influence of the loader on the wall, at least for this application. Just a thought. I would appreciate any comments.

 

[BigH]

SirAl - agree with you - I just said it differnt - i.e., focused on a smaller area. Also to keep in mind if the wall doesn't "move" - then traditionally, the loads have been "doubled" - mirror effect (although I have seen some recently questioning this).

 

[JedClampett]

SirAl, good point. I've thought about the same thing. But don't forget that H20 loads are point loads also. I suspect that concentrated loads quickly distribute through the soil matrix and become pressure loads.

 

[BigH]

Actually, I have believed that "uniform" surcharge loadings are used for such because, say you have a traffic jam on the bridge or approaches - then with "all" the wheel loads considered concurrently, it becomes more like a uniform loading - or many point loads that appear to be uniform. In other words, we aren't talking about an individual truck, but the aggregate of many at the same location. With the scenario given, there would only be, say, one tipper - so point loads or "focused" uniform load might be closer to the mark.

 

[cap4000]

First thing you need to do is get the max. front wheel weights loaded with the material. All Point Loads are then converted to horizontal wall pressures either by the Boussinesq or Spanglers method. Google Search NAVFAC DM-7 and on page 7-10-10 its already converted with the resultant effect. Good Luck.