Design Change: Soil Nail Wall into Tieback Wall
Design Change: Soil Nail Wall into Tieback Wall
(OP)
Background:
We were hired to design the structure of a soil nail wall for a geotech company. They gave us all the of the loads and the anchor locations. The soil nail wall was designed per ACI as mentioned in the below threads and was to have a shotcrete temp facing and a concrete permanent facing.
It went through a county hired review firm here in California and they want it to be stressed tendons...which would change it to a tieback wall.
per threads
http://ww w.eng-tips .com/viewt hread.cfm? qid=59653& amp;page=8
http://www .eng-tips. com/viewth read.cfm?q id=252994& amp;page=8
ht tp://www.e ng-tips.co m/viewthre ad.cfm?qid =124597&am p;page=405
h ttp://www. eng-tips.c om/viewthr ead.cfm?qi d=43703&am p;page=617
and this companies publications
http ://www.sch nabel.com/ files/publ ications/r f4b0314318 ddce/Contr actor%20De signed%20T iedback%20 Retaining% 20Wall.pdf
Questions:
How does this change my design? Can I still use shotcrete and a concrete face or do I have to incorporate a soldier pile system as mentioned in the above threads? Or is this simply going to change my design loads at each tendon location because of the stressing and the design of the structure would be the same?
Thank you for your time. All insight is greatly appreciated.
We were hired to design the structure of a soil nail wall for a geotech company. They gave us all the of the loads and the anchor locations. The soil nail wall was designed per ACI as mentioned in the below threads and was to have a shotcrete temp facing and a concrete permanent facing.
It went through a county hired review firm here in California and they want it to be stressed tendons...which would change it to a tieback wall.
per threads
http://ww
http://www
ht
h
and this companies publications
http
Questions:
How does this change my design? Can I still use shotcrete and a concrete face or do I have to incorporate a soldier pile system as mentioned in the above threads? Or is this simply going to change my design loads at each tendon location because of the stressing and the design of the structure would be the same?
Thank you for your time. All insight is greatly appreciated.





RE: Design Change: Soil Nail Wall into Tieback Wall
Soil nails are not tieback anchors. The entire nail length is bonded to the soil similar to a reinforcing bar in concrete. Soil nails do not have an unbonded length like tieback anchors. Therefore, if you pre-load a nail, you may be loading only the portion of the nail immediately behind the facing, but in front of the failure plane. Therefore, the pre-load may not reach the area of the nail that provides the majority of the wall support.
www.PeirceEngineering.com
RE: Design Change: Soil Nail Wall into Tieback Wall
Thank you for your post!
RE: Design Change: Soil Nail Wall into Tieback Wall
Check out FHWA's, AASHTO's, and CALTRANS' bridge and anchored wall design manuals. Check out FHWA and PennDOT design manuals for soil nail wall design guidance. I would expect CALTRANS to have a similar soil nail wall manual too. You need more help than can be provided in a forum.
www.PeirceEngineering.com
RE: Design Change: Soil Nail Wall into Tieback Wall
The FHWA facing design is a bit of a black box that makes many assumptions that are not obvious (I think some are wrong, but that is another story). When I use a shotcrete facing for an anchored wall I design the facing as a 2 way slab using the ACI318 direct design method with loading half of the apparent pressure.
RE: Design Change: Soil Nail Wall into Tieback Wall
www.PeirceEngineering.com
RE: Design Change: Soil Nail Wall into Tieback Wall
RE: Design Change: Soil Nail Wall into Tieback Wall
www.PeirceEngineering.com
RE: Design Change: Soil Nail Wall into Tieback Wall
RE: Design Change: Soil Nail Wall into Tieback Wall
For this hybrid system, I would think the facing would have to be very thick and much more heavily reinforced than a traditional soil nail wall. I'm picturing something like the concrete anchor blocks used in landslide stabilization. Either that, or the tiebacks would need to be very closely spaced. Either way it doesn't sound like a more economical solution than using traditional methods.
RE: Design Change: Soil Nail Wall into Tieback Wall
www.PeirceEngineering.com
RE: Design Change: Soil Nail Wall into Tieback Wall
I was saying the FHWA equations for soil nail wall facing wouldn't apply for the original post once the 'nails' become tensioned. FHWA doesn't have design criteria for what the original poster was asking I was simply telling him how I have done them.
I agree, not the cheapest system out there, but sometimes the most economical doesn't work/fit/whatever and something different is needed.