I have a stacked stone gravity retaining wall with 10 degree sloped backfill. What height of backfill do I use to calculate the soil pressure on the wall?
That suspiciously looks like a manufactured standard segmental retaining wall (SRW). Everything depends on the exposed height of the wall, if not too high. Beyond a limit, it must be designed and signed of by an engineer.
The major developers/franchisers (there are 4 of them) have great sites for general information plus engineers that are experienced internationally on many wall situations on walls up to 40' high. since you did not show a concrete footing, that is a tip=-off on the type since SRW walls do not use a concrete footing.
Dick
Engineer and international traveler interested in construction techniques, problems and proper design.
If you miss it do a search for NAVFAC DM-7 and dig for the title "soil mechanics, foundations and earth structures", or similar. It is not there in good order, but you may have to dig some through various errata, etc.
Then go to page 7-2-64 "Active and Passive Coefficients, Sloping Backfill"
There is a chart with the answer you are looking for.
if it is an MSE wall and your using NCMA design then the Ka value will be calculated using Coulomb equation which will reflect the backslope condition and therefore your height is H (the total height of the wall).
Concretemasonry - why do you say it depends on the exposed height? most design parameters for MSE (or so I thought) is based on the total height.
Also see NCMA's Design manual for segmental retaining walls.
I used the term "exposed height" since it is very close to the actual wall height that is not buried very deeply. It would take a very unusual situation and desire for absolute accuracy to change the relationship radically.
If there is a slope along the wall (longitudinal), the base of the wall can be stepped and more surgical detailed analysis can be done using the actual wall height lengths if you want to treat the soil retained as separate sections and think it can work for the site and soils.
Since all of the major systems were developed in the same market and many of the same engineers consulted for many systems if it was possible because of patent/information disclosure restrictions. That is the reason the major systems have slightly different product features, but essentially work the same in practice. - You could load a few semis with the reports and test results conducted.
I remember working with all of the major systems during the development, production problems and the first installations including seeing them delivered on a raft for an installation on a steep river valley.
Just rely on the product developers technical information/assistance, the staff support and then determine which systems are available near the project site and design accordingly. they have seen some very unique situations, having been involved in projects in more countries that I have visited (37 so far).
Dick
Engineer and international traveler interested in construction techniques, problems and proper design.
