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Senin, 06 Desember 2010

Soldier Pile Wall

mjalexan (Civil/Environme)
http://www.eng-tips.com/viewthread.cfm?qid=281487&page=1
16 Sep 10 10:07

Permanent Soldier Pile Wall
Wall height (H) = 12 feet
Using 14x73 H piles with precast concrete lagging
Deflection is limited to H/100 => 1.44 inches
Soil:
Sand = 120 pcf, phi=28 from top of wall to 21 feet
Sand = 120 pcf, phi=32 from 21 feet to 40 feet
I have a traffic surcharge of an additional 2 feet of fill behind the wall and level back fill.
I have a 14x73 H pile in the center of a 30 inch predrilled hole which will be filled with 3,000 psi concrete. I saw a thread about this but my question was not answered.
I want to determine the composite stiffness to use below the dredge line to keep my deflection down. Everything I have found online is the reinforced concrete design example with a row of rebar in the tension side of a beam, no circular shafts or columns.
Using just concrete or just the h pile seems too conservative, especially with the very limited deflection.

PEinc (Geotechnical)
16 Sep 10 12:27
FYI, I assumed that you could use Coulomb earth pressure coefficients and wall friction for both active and passive coefficients. I assumed 10' maximum soldier pile spacing. I ignored the strength of the concrete in the analysis. I assumed a passive resistance width of 3b = 3 x 2.5' = 7.5'. I added a Boussinesq area surcharge of 240 psf (= 2' x 120 pcf) starting 1 foot off the wall and extending 25 feet back. Using an HP14x73, GR50. I get an deflection of 0.99 inches. In my opinion, your 1.44 inch maximum allowable deflection (H/100) is not very limiting. I would design a permanent wall for less deflection than that. I would probaby design for no more than an inch unless specs required less.

Also, if you are using precast lagging, I hope you are building a fill wall where you can stack the lagging from the bottom up. It is hard to install concrete lagging in lifts as the excavation is being made. If you are building a fill wall with drilled soldier beams and concrete lagging, you probably are building an uneconomical wall.

dcarr82775 (Structural)
16 Sep 10 13:42
The only way to reliably get composite action between the H14 and the concrete pier is to use Shear Studs, or some type of shear lug. My experience is that contractor's hate doing this so I assume no composite action and use a beam sized with that in mind.

msquared48 (Structural)
17 Sep 10 22:42
Considering the low strength of the concrete encasing the pile so it can be easily removed to install the lagging, I would not rely on any composite action of the W shape with the 30" concrete pile.

If you are placing a permanent concrete foundation wall next to the W shapes, then composite stud action will work to attach the p[ile to the concrete wall, but, since the W shape is already loaded laterally, the composite action will only affect lateral deflections if the wall is further loaded laterally.

Have you considered using soil arching action to decrease the lateral load to the pile. If not, ask your geotech.
The load reduction may give you the lateral deflections that were recommended.

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