Geogrid installation questions
Geogrid installation questions
(OP)
Proposed benched/ terraced segmental wall.
1. Is there any geo/struct concerns with geogrid reinf from one wall extending laterally below the next benched wall and so on to meet its design length. The intent is to minimize the bench spacing thereby minimizing loss of backyard.
2. I have never seen this and will likely reject it but need basis: can a grid have a batter to it, and if so what are the limits. I expect it needs to be placed/taut in a flat position throughout.





RE: Geogrid installation questions
With respect to your second question, the grids should always be installed horizontally.
RE: Geogrid installation questions
RE: Geogrid installation questions
2. I thought I had seen someone referring to sloped grids on here and saying it was OK. Might be wrong on that. If anything, they should not slope up from behind the wall face. As for a basis to reject it: Ask to see the calcs performed for internal stability using a slope on the grids. Most, if not all, computer programs for MSE walls model the grids horizontally, as they are typically installed. Unless they can show numerically that it works, reject it.
RE: Geogrid installation questions
If there are a lot of tiers, and none are of great height, the design can be analysed as if it were a steep slope with a face angle represented by the tier height and offset distance.
I would very much disagree with the idea of modelling the structure as single height vertical wall for global stability purposes. First of all the locus of maximum tension will be in the wrong place and you may well overstimate resistance to pull out. A better method is to model the vertical stresses as you would for any embankment structure with sigma zero falling along the tan phi line and sigma max falling along the 45 degrees + phi/2 line. Once you know the vertical stress distribution working out tmax layer by layer is the same as a normal MSE retaining wall.
Finally, with respect to not allowing reinforcements to be downwards sloping - providing the down slope is modest (say 5-10%) and L is a section length rather than a true length,there is no reason to reject it. Actually it is quite a good idea to provide a slight bacakfall to the filling operation since it helps drain rainwater away from the facing during construction. And - by the way - if you wouldn't reject it for soil nails why would you reject it for grid soil reinforcement?
RE: Geogrid installation questions
I agree: "I would very much disagree with the idea of modelling the structure as single height vertical wall for global stability purposes."
I said: ". . . internal stability by making one wall the height of the combined piers. Once the grid lengths are determined there, check the global with the proposed profile."
RE: Geogrid installation questions