Soil Nail Wall Partial Cut/Fill

[jdgengineer]

We are working on a residential project where the basement walls are proposed to be supported with soil nails. These will be designed by another engineer who is also doing the temporary shoring design so the soil nails will serve as both the temporary shoring and then have an embed plate cast into the permanent retaining wall to brace for the permanent condition.

There are some sections of the wall where the civil engineer is showing approximately 2-6' of fill above the existing grade.

I'm trying to understand how this would work with a soil nail wall.

I know roadway construction sometimes uses a MSE wall above a soil nail wall in similar conditions but I'm not sure how feasible that is here.

We will coordinate this with the other engineer who is designing the soil nails but just want to come with some ideas.

Could the top row of nails be designed for the extra retaining height and have the permanent wall cantilever above the top row? Could the fill be CDF or geofoam instead to reduce the active pressure and then just have the soil nails designed for the additional surcharge of the CDF?

Or are there other approaches to using soil nails in partial fill condition? The temporary shoring would not have any fill, just the permanent wall.

 

[EireChch]

I am struggling to understand the problem here?

Is it that the soil nails need to be made longer to accommodate the 6' of fill at some locations? If so what is wrong with that?

 

[KootK]

Could the top row of nails be designed for the extra retaining height and have the permanent wall cantilever above the top row?

That's what I imagine happening.

 

[jdgengineer]

I am struggling to understand the problem here?

Is it that the soil nails need to be made longer to accommodate the 6' of fill at some locations? If so what is wrong with that?

My description probably wasn't very clear, but the finished grade in some portions are 6' higher than the existing grade. My understanding is that soil nails are only installed into the existing grade so the permanent wall would be 6' taller than the temporary wall. If the top row of soil nails is 2'-6" from grade that means they are 8'-6" from top of permanent retained heights.

That's what I imagine happening.

That's what I am hoping they can do, I'm just not sure if that is too much load for the top row of nails. The nails are spaced 5'-0" oc each way so those top row would have a lot more tributary.

I'm wondering if it would be more appropriate to have the fill material as geofoam or something more laterally stable to reduce/eliminate the active pressure on the taller wall.

 

[KootK]

I wouldn't sweat the geofoam until the designer of the nails actually says it's a problem, especially if that designer is someone that you're able to communicate with now.

 

[jdgengineer]

I wouldn't sweat the geofoam until the designer of the nails actually says it's a problem, especially if that designer is someone that you're able to communicate with now.

Yeah, I'm not. I just wanted to have some ideas together for when I talk to him just in case we need to explore alternatives.