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Wall Construction

Wall Construction

Wall Construction

(OP)
Hello,

I'm a Civil/Site Engineer and I'm currently dealing with the permitting process for a residential subdivision. The access road to the subdivision requires a 30-foot high retaining wall to be constructed in a cut. The soils are very course sand overlaying course gravely sand. The problem I've ran into is that I'm not sure how to generally construct this wall. How would the excavation be stabilized? Would sheeting be used? Shoring? The cons. comm. does want some sort general explanation. Any thoughts? I've attached a cross-section.

Thanks!

RE: Wall Construction

It may be helpful if you talk to a construction  contractor in the area to get their opinion about how to approach it. I think there are several ways to accomplish it.  

The first idea that came to my mind is to overexcavate behind the wall then fill it in and compact as you build the wall.  

RE: Wall Construction

Drill holes for auger cast piles and use top down construction.

RE: Wall Construction

30 foot high shoring will probably cost you around $50 per square foot which is $1,500 per linear foot just to construct the shoring system. At that point you may as well just build a concrete facing and leave the shoring in place. Another option is to excavate the 30 feet and lay it back at 1:1 or flatter depending on your safe angle of repose. If you do that, you may want to step your wall back so you don't have to backfill as much.

RE: Wall Construction

There are many different ways to do what you're proposing.  If you have the room to lay the soil back with an open cut then build up your MSE wall it will probably be cheapest.  But that will require you to slope a long way from the back of the geogrids up to existing grade.  I don't know if you have that kind of room.

It usually doesn't make sense to build a top-down wall only to place a bottom-up one in front of it.  As others mentioned above, soldier beam and lagging or soil nail walls can be used for permanent applications.

As for price, it will vary greatly depending on the size of the job, subsurface conditions, access, location, and whether union or open shop labor is used.  It may end up being a little cheaper than cvg's $50/sf.  It may end up being a whole lot more...

RE: Wall Construction

LC06

No expert here. But I will try to help.

Has the block wall "system" been designed yet? If so you should have strap length and locations of lengths for a given height of wall (hW). This will give you the actual work excav. limits required to construct the wall. And maybe this has been done and your sections are to scale.

I think you are going to need some geotechnical data on the soils of your cut.

I would use the sheet pile, make the cut, then build the wall, place fill in area between proposed top of wall and behind sheet face, place top soil and establish good vegetative in this area, remove the sheets.

RE: Wall Construction

LC06,

Call Moretrench in Assonet, MA and Schnabel Foundation Company in Southborough, MA.  They may be local and can give you design-build proposals for a permanently tiedback or soil nailed wall.

RE: Wall Construction

One more thought:

That's a pretty high wall for one to design if he has not done that much before.  I'd let someone else take responsibility for it, specifically an experienced  contractor

Sometimes for public type work you might just bid the idea with the final result specified as to the wall dimensions and location. Then, require the contractor to design and build it at his fixed price with a guarantee as to structurally capability.  That way you don't design or take responsibility for it, since that is not your expertise. Of course require the designer to be fully licensed,etc.

The types of firms mentioned above are the kind you should use with provided evidence of past similar work.  This way you get the wall you want at lowest cost.

RE: Wall Construction

I agree with born2drill.  Soil Nails or permanent soldier piles.  You might leave it to a design build contractor though.  Depending on where you are a local contractor of one kind or another might have significantly lower mobilization costs.  It's a small wall, leave it up to the market...

RE: Wall Construction

Just remember, LCruiser - you get what you pay for.  Watch out for cheap prices from contractors who are in over their heads.  PEinc named two excellent companies.  (one being my former employer)

If LC06 let us know where this project is, many of us here could get him in touch with the right people in his area....

RE: Wall Construction

LC

if I were the owner, there would be a Mech Stab Earth wall (like you see on highway projects) the block wall (my opinion only) is only for 6-7 foot heights.

I have seen others build them 30 ft high. I would not. Several potential issues. $$$$$, maint., closely monitoring.

RE: Wall Construction

I'm with several others here, I'd look for design-build services, with either soil nail or soldier-pile and permanent tiebacks.  A cast-in-place permanent facing can be used with soldier piles, while soil nailing more often uses a gunnite facing.  With clean sands and gravel, there may be difficulties either way in maintaining short-term stability of the cut face.  Excavation support contractors can provide some details as to how they'd handle it.

RE: Wall Construction

Solider pile or sheet pile would be my initial considerations.  Assuming aesthetics aren't an issue, my experience is that a high section modulus cantilevered sheetpile would go quicker during construction.  If your preliminary design crests over into tie backs, I'd look at solider pile.  I had Schnabel on a solider pile project, no faults except they kept pushing for high strength tie backs to increase spacing & reduce # of  piles.  One might call it value engineering, another might call it reducing your factor of safety.

RE: Wall Construction

I'd go design build. Wish what you want on paper (i.e., top of wall, bottom of wall, grades,etc.) and have the contractor submit sealed design drawings and have the onus to put it in place.

Bear in mind that if you are cutting close the property line, the availability of a construction easement may allow for greater options in the contractor's approach.

f-d

¡papá gordo ain't no madre flaca!

RE: Wall Construction

IMHO, 30 feet is too high to consider cantilevered sheet piling.  It could be quicker but it would be very heavy, very long, very expensive, and would probably deflect too much (unless, again, it is even longer, heasvier, more expensive).

As I said before, call Moretrench and/or Schnabel for a design build proposal.

Also, "high strength tie backs to increase spacing & reduce # of  piles" does not reduce the safety factor.  This statement is more likely to indicate limited tiedback wall experience from anyone who believes the statement.

 

RE: Wall Construction

Right.  Fewer tiebacks with higher capacity will in most cases be cheaper and faster, but certainly no less safe.  Ground anchors are one of the most reliable construction techniques out there.  Remember every one is tested!

Also, the necessity for tiebacks isn't what determines whether you use sheets or beams.

RE: Wall Construction

Looking at your worksheet, it appears that the design is with doublwall.  If you are from the North East, contact Atlantic Pipe Corp in Plainville,Ct since they design and build such retaining walls. Doublewall is an excellent product.

RE: Wall Construction

It doesn't matter if the wall was originally designed for Doublewall.  You would still need another temporary sheeting wall to build the doublewall.  Therefore, the originally designed wall is not economical.

RE: Wall Construction

Give you another thought on your wall. You might want to look at doing a secant pile wall. Then you can design the strength you need for minimizing the tie-backs with the use of either HD beams or extra rebar in your columns. The other replys are right, get an experienced contractor. Moretrench and Schnabel are both good. You might also look at Remedial Construction Services, (RECON) out of Houton Texas also. They have offices all over the U.S. now. I'm sure they can cover you where your at.

RE: Wall Construction

I'm not sure why everyone is so in love with the secant pile wall lately, but I'd venture to say that a secant wall will be way beyond the budget for temporary earth retention on a residential subdivision.

RE: Wall Construction

I agree with born2drill about secant pile walls.  However, I thought this wall was to be a permanent retaining wall along a driveway cut into a hillside.  Very few residential developments need or can afford a wall this high.

born2drill, did you work for SFC or Moretrench?  Which office and when?

RE: Wall Construction

Get hold of Doublewall in Plainville,CT.  Their retaining walls are used on many private and state projects.   

RE: Wall Construction

I would think that Doublewall would be the wrong wall to build in a 30' cut, maybe even a higher cut if the ground slopes up behind the rear end of the Doublewall blocks.  You would still need a tiedback temporary sheeting wall.  In addition, I'm not sure if Doublewall can go 30' high.

Why build two high walls when you can build just one?

RE: Wall Construction

I'm always somewhat skeptical when I'm told that I *have* to use one proprietary product or another.  There are many, many techniques for earth support and what is economical in one case or for one contractor might not be for another.

PEinc - I used to work for Moretrench in NJ up until about '05.

RE: Wall Construction

born2drill,

Then I probably know you.  What retaining wall projects were you on?

RE: Wall Construction

Oh boy... what retaining wall project wasn't I on?

Bank Street Commons, Bronx Criminal Courthouse, PA Rt 309, The Siena in Montclair, NJ to name a few.  Sound familiar?

RE: Wall Construction

One of the projects was the expansion of I91 in Bridgeport, CT where some heights were at least 25'.

RE: Wall Construction

Oops,I95.

RE: Wall Construction

born2drill, I designed the sheeting and soil nailing for Bank Street, Bronx Criminal Courthouse, Route 309, and The Siena.  Now, you must know me.  Who are you?  Take of your mask!

RE: Wall Construction

No, I have no idea who you are. I did not design this wall nor was I involved in its erection. It was erected back in the 90's and at that time, it was a great looking impressive retaining wall. I worked there in an another capacity, however, on construction sites tradespeople are not blind about the work of others.  

RE: Wall Construction

chicopee, please pay closer attention.  My previous comments were clearly addressed to born2drill.  I'm sorry if I confused you or anyone else.

RE: Wall Construction

born2drill, are you Frank V.?

RE: Wall Construction

Ha, no.. good guess though.  He left a little before me.  After I saw your profile I realized who you were.

I work with Andy P now.  Does that get you there?

RE: Wall Construction

Nolan!

RE: Wall Construction

You got it, John.  Boy, we really hijacked this thread, didn't we?

RE: Wall Construction

I guess it doesn't matter much that we hijacked the thread.  The original poster never participated after making his original post in JANUARY!

Now, don't you be spying on me in these forums!

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