Soldier Pile Wall - with concrete panel lagging 1

[BurgoEng]

I am designing a Soldier Pile retaining wall for a roadway with a change in retainment from 5ft to 30ft. We want to use concrete panels for the lagging rather than timber as this will be a permanant structure, but several searches on Google turn up nothing useful as far as manufacturers go. Does anyone know of companies that do this? We are thinking the panels would be similar to those used for sound barriers on highways, but we need to show details and manufacturures on our drawings.

 

[PEinc]

Precast concrete panels are NOT the way to go unless (1)the wall is a total fill wall, (2) unless you can totally and safely open cut to subgrade so that you can stack and backfill the panels from the bottom up, or (3) unless you use timber lagging as you excavate from the top, proceeding downward, with the plan to attach a precast facing after the wall is built.

Precast plank lagging installed from the top down as you excavate is an extremely bad idea - especially if you have a tiedback wall.

Before you design any precast lagging wall, talk to the specialty contractors who may build the wall. They will have opinions on the use of precast.

 

[DRC1]

I agree with PEInc. One option would be to build a soldier beam and timber lagged wall. Then add shear studs and pour a conc. face.

 

[DaveVikingPE]

I was involved in a project similar to (2) described by PEinc. Precast was used. However, it was designed specifically for the project. Very difficult, painful project.

 

[PSlem]

I've also done one this height with shotcrete and soldier piles. Cheaper than a one sided form and shear studs on the piles.

 

[PEinc]

I agree with the above comments.
Install corrosion protected soldier beams.
Install timber lagging. Pressure treatment usually not needed.
Install corrosion protected tieback anchors whenever the lagging reaches a tieback grade.
Continue installing lagging and tiebacks until subgrade is reached.
Install a premanent facing: either CIP concrete, shotcrete, or a mechanically connected precast facing (which is my personal last choice).
Don't forget to address wall drainage using some product like MiraDrain applied against the lagging, between soldier beams.
Also, a tiedback wall should not use tieback wales which will interfere with the facing. Use some type of thru-beam connection or double WF or double channel sections so that the tiebacks can be installed between the two members that comprise one soldier beam.

 

[BurgoEng]

Oh boy... you've all given me plenty to think about. Having never (personally or within the company) done ANYTHING remotely close to this design, it seems as though we had already planned to do everything you all say to NOT do....that being we planned on using precast concrete lagging, double channel whaler on the outside of the wall (which would interefere with the lagging) and assumed the lagging could be loaded from the top and dropped down during excavation.

I was working on a spreadsheet to help with the calculations as we don't have any software to handle this type of work. Would some out there mind taking a look at it for me to see if it makes sense.

We planned on using Chance spiral anchors as the support, roughly 6 ft from the top. Would they be someone to call and chat with about the best way to go about this design/construction?

Thanks for all your help...I have a feeling this message board will be coming in quite handy in the future.

 

[PEinc]

BurgoBertin,

If you are a consultant doing the design for the owner, call a specialty, design-build contractor who is very experienced in tiedback walls. They would like to help just to get the lead on the job. Where are you located?

Google "Peirce Engineering, Inc."

 

[shepherd]

BurgoEng,
Check out the geotechnical engineering circular no. 4 put out by Federal Highway Adminstration. I believe it will give you what you are looking for.

http://www.fhwa.dot.gov/engineering/geotech/library_sub.cfm?keyword=020

 

[BurgoEng]

PEInc,

We are a civil design firm (mostly grading, drainage, traffic, site develop/planning, small 1 story structures). I was recently brought in to help in expanding structural design capacity, but my background is in Power so this stuff is all new to me.

We're in Northern NJ. The job is North Bergen, NJ, right along the Hudson River. I'll try getting in contact with Peirce to see if they'll lend some advice. I took a look at their site and they have pic of a NJDOT job with tie-backs that looks roughly like what we were aiming for initally.

 

[PEinc]

That's me.

 

[BurgoEng]

PEInc,

We are trying to get Chance Anchors in to give a presentation about their anchors and about the design of the wall in general, is this something that Peirce would be able to or could do? I am not privy to how contracting out work is organized as I never get involved in contracts (thankfully) so I dont know if asking this would be some sort of conflict of interest or if Peirce would just not be interested in consultation if not part of the contstruction, contract or otherwise. Options?

 

[PEinc]

Call me.

 

[yakpol]

PEinc,
Do you have by a chance a detailed design criteria for tieback wall based on AASHTO LRFD? This part of code is written so poorly...

Thanks!

 

[PEinc]

yakpol,

I've designed a number of temporary tiedback walls using LRFD but no permanent walls yet. There is much confusion in how to design these walls with LRFD. I'm not sure that any two engineers are doing it the same.

Use the appropriate earth pressure diagram. FHWA shows the new non-symetrical trapezoidal pressure distribution for both single tier and multi-tier tiedback walls. The shape and magnitude now depend on the tieback locations. FHWA tried to "fix" something that wasn't broken when they changed the trapezoid shape and derivation of the maximum lateral earth pressure.

Get your unfactored pressure diagram and surcharge pressure diagram. FHWA show you how in Engineering Circular No. 4. Apply the appropriate load factors and size your soldier beams and wales using the appropriate resistance factors. At this point, the determined tieback loads are factored loads. Since tieback anchers are field tested to a higher load to confirm a safety factor, you can't use the factored tieback loads for anything other than for sizing the wales.

I usually also design the wall with unfactored loads (ASD)to get the tieback anchor service loads which are then used as the tieback design loads. The tiebacks are then tested to about 133% of the unfactored design loads.

FHWA has screwed up tieback wall design. Now, the state DOT's and AASHTO have to follow FHWA.

The bottom line is this: Soldier beam and wale sizes may decrease slightly under LRFD. However, this decrease may be offset by the "new" trapezoid shape and the high load factor for live load surcharge. Tieback loads for the upper tier probably increase due to the new trapezoid shape which is now somewhat top heavy. Design time, design cost, and review time are increasing. Tieback anchors to date have been designed and tested using safety factors on the tendon steel and the bond stresses between grout and the soil or rock. There is no tieback design method or testing method that uses LRFD. If you determine a factored tieback load and then test it to a higher test percentage, you will be greatly overdesigning the tiebacks and the wales.

 

[yakpol]

PEinc,
Thank you very much for so detailed answer. I did follow FHWA circular No. 4 (allowable stress design) applying LRFD factors. The main confusion was trying to interprete the geotechnical company recomendations (given for allowable design) in the right way: like kickout criteria and passive earth pressure resistance factor for service and strength limit states.
Thanks for great help!