why "surcharge" for an empty log truck? i ask that question meaning that i'm fairly certain the concept of surcharge would not really "work" for an empty log truck. if an empty log truck can "put a kink" in the design of whatever you're looking at, you're thinking way too hard about it. perhaps a few more details might help me understand what you're trying to accomplish.
As is often true for any structure, the most dangerous time for the structure is during construction. This is especially true for retaining walls and similar structures. During construction, heavy equipment may be operating close to the wall imposing large "surcharge" loads, impact loads and similar forces on only partly consolidated backfill. It seems highly unlikely that any of these loads would be smaller than an unloaded log truck.
I agree with miecz, when your talking roads your into AASHTO design. AASHTO specifies 250 psf. To think that the only vehicle to ever traffic over the wall would be an empty logging truck is a bit aggressive - what about when the fire truck arrives?
I appreciate the comments and maybe I should have described the circumstance a little better from the start. I am designing a small ramp that will tie into an elevated (about 5' high) concrete pavement surface. One side of the ramp will have a shoulder and taper off into maybe a 3:1 slope while the other side will have a retaining wall. This will be located on an installation where it is anticipated that only empty log trucks will operated. I have designed a retaining wall five (5) above grade with a live load surcharge pressure of 250 psf in hopes that this will cover the vehicle loading. I do not deal with vehicle loading too much and therefore have not invested in an AASHTO manual so whatever suggestion you can give or have given s highly appreciated-thanks.
I appreciate the comments and maybe I should have described the circumstance a little better from the start. I am designing a small ramp that will tie into an elevated (about 5' high) concrete pavement surface. One side of the ramp will have a shoulder and taper off into maybe a 3:1 slope while the other side will have a retaining wall. This will be located on an installation where it is anticipated that only empty log trucks will operated. I have designed a retaining wall five (5) feet above grade with a live load surcharge pressure of 250 psf in hopes that this will cover the vehicle loading. I do not deal with vehicle loading too much and therefore have not invested in an AASHTO manual so whatever suggestion you can give or have given is highly appreciated-thanks.
oh i see...we're talking two different "surcharges". i was interpretting this as preloading to minimize settlement of the final structure. my misunderstanding...i do let the contractor lingo get the better of me sometimes.
If the trucks are highway legal, which they should be when empty, then I would look at the AASHTO spec mentioned above or the 0.8m of fill given by CSA S6 (or other appropriate code depending on jurisdiction).
I also think how likely it is that full trucks would ever pass by the wall needs to be looked at, if they are not highway legal loads.
