temp. retaining wall using a beam in concrete and 1" 'street plate' 6

[ewhpeps]

I need advice on designing a temporary retaining wall on a construction site. I want to utilize the H-beams (W27x102)that extend out of 48" diameter concrete shafts (secant wall) approximately 3' to prop up a 'street plate' 8'x20'x1".

So the retaining wall will be 8' high with the bottom 3' supported by the H-beams that are spaced 3' on center. Behind the wall, engineered fill will be placed to the top of the wall then sloped another 2' for a total height of 10'. Once up to grade, a delmag RH32 drill rig (143 kips/track) will crawl out and drill a wall of sand shafts that is 10' offset of the secant wall. The edge of the track of the drill rig will sit within 1' of the top of the slope and be approximatly 3' away from the wall.

I attached a sketch of the design but the 1" plate is only 8' high so the top 2' will have to be sloped from the top of the wall to get the full height and the rig will have to be moved over 2 more feet.

 

[csd72]

You will effectively have punching shear at the top of that plate where it interacts with the Hpile and this needs to be allowed for.

You also need to check the high weld stresses at the weld between the Hpile and the plate.

Have you checked the weight of this thing?it sounds very very heavy and may require special lifting equipment (crane e.t.c.)

For the cantilever bending you will have an effective width which will be much less than the width of the plate.

You have not shown the extra 2' of soil and this needs to be allowed for as a surcharge.

How are the sand columns compacted? If it is by any dynamic means then you may get additional loading from the rig when the weight is dropped e.t.c.

 

[oldestguy]

It appears that this will be abandoned in place. If it has to continue to do its job later, are there corrosion issues? If I was doing the welding, I'd really have a rough time standing on my head for a bead along the under edge of the plate. Not easy. Ya gotta see what goes on to do the job right especially for that location.

Have you considered some added bracing, say a 3" dia. pipe from the outboard flange of the H pile up to say 2/3 up the side of the plate, as a strut to take away the bending problem at the connection of plate to pile. This would permit the plate to sit higher in elevation also.

 

[ewhpeps]

no welds, this wall will be temporary for the drill rig to drill the sand trench. the 143k includes the extraction force for drilling. I need to calculate the magnitude and location of the horizontal force on the wall due to the surcharge of the drill rig and the horizontal force of the soil on the wall.

 

[PEinc]

Your scheme looks like an accident waiting to happen. An 8' high soldier beam wall should not need W27x102 soldier beams, with 48" shafts, at 3' on center. Even if the plate does not experience punching shear at the top of the soldier beams, what will keep the plate from flipping over the soldiers?

I suggest you hire someone with experience in designing shoring walls.

http://www.PeirceEngineering.com

 

[ewhpeps]

The piers and beams are 3' on center and the main purpose is for a secant wall that is drilled 80' down. The temporary retaining wall using the street plate is so the drill rig can drill the sand shafts from a higher elevation.

I guess your question is the one I am trying to answer...Will the wall overturn?

I attached a better sketch that is closer to something feasible.

 

[dcarr82775]

Looks bad to me, and the 1" plate feels terribly undersized to cantilever 7' with that kind of surcharge. Without running the numbers I think it has a good chance of overturning. If it doesn't actually overturn it will shift a fair amount just to mobilize the passive pressures at the bottom of the plate.

Can you weld some extensions onto the top of the W27's?

 

[ewhpeps]

only cantilever 5' but the general concensus is for bracing. I was hoping to not need welds.

I will probably design something at a 45d angle off the back of the beam to about the midpoint of the street plate.

 

[PEinc]

Is the engineered fill a temporary condition? Does it eventually get removed? Do you eventually excavate down in front of the secant pile wall? Is so, why don't you just drive some cantilevered soldier beams in front of the secant pile wall (at about 8' on center), stack some lagging between the soldier beams, make your fill (which will temporarily cover the W24's), drill your sand shaft, and then remove the fill and the soldier beams?

http://www.PeirceEngineering.com

 

[dcarr82775]

The 2' of 1:1 slope above the plate removes virtually no soil load. As far as the load on the plate is concerned it might as well be cantilevering 7' above the steel beams.

Use a Boussinesq distribution to determine the loading on the plate from the crane. It is conservative, but with a heavy piece of equipment that probably costs a fair amount of money, conservative is good.

 

[oldestguy]

If you don't at least do some welding of the plate(s) to the H pile, then your strut won't work. Ya gotta develop some bending resistance at the top of the H pile area in the plate-strut combination. Put the strut in compression and the plate in tension there. Do at least a weld bead along the top of the H pile flange, which later can be cut free with a gouging torch. Of course some stress calculations needed. If properly strut braced, you may not need two plates.

I'd secure that rig to some anchor off to the right of your drawing. No point in having it side off the bank.

 

[csd72]

As others have indicated the retaining wall is probably unnecesary. Why not drill the secant piles from the lower level and if necesary leave the cage sticking out the top and use a sonner tube to cast the final section.

 

[wmta]

The system you have will not work, too much deflection. Get some help

 

[ewhpeps]

This is a temporary condition but not feasible to use the soldier beams. Contractor is trying to make use with material onsite.
The secant piles are being drilled right now. The beams are placed inside the shaft and then it is filled with concrete. Once the secant wall is complete (2 weeks), the plates will be placed against the beams and braced (somehow) so the fill can be brought up to elevation so the sand shafts can be drilled and finished at the proper elevation.
Stay posted, I have a dwg that I am working on that will detail the wall and I will post it tonight or tomorrow.

 

[SixDegrees]

ewhpeps: You should develop some basic lateral earth pressure diagrams. You have a 5 foot cantilever wall with 3 foot of embedment, holding back 7 feet of soil with a 147 kip surcharge. Using a triangular earth pressure + the Boussinesq surcharge load (which will be greater nearer the top of the wall than at the bottom) the resultant is most likely above the top of the secant wall. The bottom of the sheets will try move into the soil creating a more complex earth pressure distribution (passive on the bottom and active on the top). This approach will at least enable you to calculate the bending forces on the sheets.

Consider, much wider mats to distribute that crane load, maybe even using those steel plates for that purpose, and driving in some stiffer deeper structural elements. If you do this without calc's those bigger mats (ones that bridge between both tracks) may be all that save you from disaster.

You also need to be darn sure that that secant wall was designed for the crane being that close to it.

 

[ewhpeps]

Here is a scale dwg with dimensions, still struggling with the calcs.

 

[ewhpeps]

don't know if anyone can view this, but I attached a picture of the site. In the picture you can see the drill rig and the beams sticking up at the bottom of the blue ladder.

 

[dcarr82775]

A couple of things,

- I can't see that the #11 bar contributes anything. I think it actually hurts things.
- You do not show any welds, but I assume there are some (there need to be)
-weld the diagonal C6 to the W27 web, not the flange
-The horizontal C6 'waler' isn't going to do much bent about
its weak axis, if you need a waler, provide a real
serviceable waler

- Get somebody involved who knows shoring work to help you out.

 

[PEinc]

I agree with dcarr82775 about the C6 wale, #11 bar, and welding. However, I would not use the C6 brace between the top of the W24 soldier beam and the plates. I would use a T-section cut from another piece of W24. I would weld T-flange to front flange of W24 soldier beam and weld the web of the T to the web of the soldier beam. I would weld the web and flange of the T to the plate. With such close spacing of the soldier beams and T-section braces, you may not need a wale.

http://www.PeirceEngineering.com

 

[DRC1]

I agree with PEinc and dcarr82775 - you really should get someone with retention design experience. This forum is a great place to learn new things, but a dozen posts will not give you a viable design. Loads need to be computed, and the effect of adding 143 kips will not only effect the temporary retention system but the permanent wall. Since this system is being used to advance the permanent wall, the effects of limited curing of the concrete need to be included in the design of the system. Further drilling down 80 feet will require a stable platform. any deflection of the temporary system will cause the rig to skew, which can lead to whole host of problems.
I am not saying you don't have a good concept. What I am saying is that I have done shoring for over 20 years, and you need to take your concepts to an experienced shoring engineer who can design the system to do what you want to do. The members of this forum have great ideas based on a lot of experience and can give you good suggestions, but not a complete design, which what you need.
I offer this post with great respect to everyone in this forum, including ewhpeps, and hope I have offended no one. My fear is that with out a proper design someone could get hurt.