15m dia steel bin retaining wall (biggest gabion ever?)

[deckard452]

Yep, you heard right.

I'm desining a 15m (metre - say 50 feet) tall by approx 50m (165 feet) long retaining wall on a mine site so that ore trucks can back up and dump ore into a hopper that feeds a crusher.

Normally these are done with reinforced earth strapped back to solid anchors or a concrete structure. In the remote parts of North Western Australia, concrete is extraordinarily expensive. So steel must be used wherever possible.

The client has his mind set on a new approach (I've never seen it before). Basically, construct two 15m diameter steel tanks (8-10mm wall thickness) 15m tall side by side. Then each side of that you have two smaller (13m dia, 13m tall) tanks. Fill and compact local soil in the bins which will now act as a very large gravity retaining walls. A straight edge for dumping is given by bridging between the tangent points on the larger tanks and dropping a number of heavy steel columns to reduce the loads

I have problems relating to how these will work with regard to ovaling under asymmetric loading, local wall stresses under global bending + the weight of a large concrete apron on top plus the 400 odd tonne haul truck. I also need to consider the draw down forces of friction during compaction increasing the compression in the shell wall.

All this, let alone the issues of how do you construct these.

I'm not asking for an answer to all my questions here but does anyone know of this system being used anywhere - ever?

Even better would be a case of somebody considering it but discounting it for whatever reason. I've tried the cost side of it but the client is convinced it will be cheaper.

 

[aggman]

The tanks have h/d ratio less than 1.5, so they can be designed using Rankine methods. The loads should be pretty much distributed as a surcharge since you have a dump pad on top, and I would make sure that it was rigid enough to insure the load from the trucks will be spread out. So what you will end up with more or less is normal rankine pressures with a large surcharge in a localized area. It does not seem very reasonable to do this type of design. The construction of the tanks themselves will be very expensive to build. They will either have to be field welded or bolted, both of which are common, but not exactly cheap compared to what the cost of a tie-back wall is. I have designed several tie-back walls, one in your size range which was 50' x 120' for the same type of application. The walls have vertical steel columns anchored to a footing on 5' centers typically. The footing is generally not that large, because of the mass of the foundation under the crushers can be used to help hold the system back. To tie the columns together we use either timbers or steel beams horizontally, depending on the life span. These are placed close enough together to ensure that the backfill material will not seep through. We typically use a large gabian stone to ensure drainage. The vertical columns are then tied back to abutments, or rock and soil anchors. (We have even used pipe in the passive zone for anchors.) We use tiebacks going vertically on the columns at spacings less than 10' countinuous. This keeps the anchor loads low and reduces bending in the columns to keep them reasonable. This type of wall design cost much less than an equivalent concrete wall. The only time this type of design is not used, is when a customer demands something different, which may be your case.

 

[Focht3]

The "steel cofferdam" approach won't be cheaper. Either a soldier pile and lagging wall - as described by [blue]aggman[/blue] - or a geogrid reinforced crushed rock mass will be a lot cheaper.

Does your client own a steel mill, or wholesale steel plate? Or own a lot of steel plate that he can't seem to sell? These conditions would potentially explain the position he has taken -



Please see FAQ731-376 by [blue]VPL[/blue] for tips on how to make the best use of Eng-Tips Fora.

 

[DBNodurf]

"ensure", not "insure"
thanks

D. Bruce Nothdurft, MSCE, PE, PG, M.ASCE, etc, etc,...
Principal Engineer/Geologist
Atlantic Geoscience & Engineering
Charlotte, NC

 

[deckard452]

Jeez - fanks for that!
Me fought this woz a engine ring forum. Good job all those letters are good for somefink. Shame you couldn't comment on the topic at hand.

But hang on a mo smarty-pants! --- etc is an abbreviation of et cetera so it should have one o' them dot fingys on da end. Like this - etc.

Let he who is without sin cast the first stone. And people who live in glass houses should get dressed in the dark.

 

[DBNodurf]

unless they look really, really good

D. Bruce Nothdurft, MSCE, PE, PG, M.ASCE, etc, etc,...
Principal Engineer/Geologist
Atlantic Geoscience & Engineering
Charlotte, NC

 

[Focht3]

Not to get between you two, but -

If you want help from the members of this forum (or any other), your written correspondence should be carefully reviewed before it is posted. Remember that our only impression of you is the quality - and tone - of your posts. I suggest that you spell check your posts; one useful product is called ieSpell (

http://www.iespell.com).

It integrates with Internet Explorer, is easy to use - and free. I highly recommend it. (I don't get any revenue from it or its' author -)

And don't be so sensitive! While some sarcasm is tolerated, but you may get red-flagged for "flaming." I suggest that you take care with the sarcasm in general; you may find your questions receive NO responses...

On the improper use of words: I would suggest a gentler tone to avoid being misunderstood. One of my pet peeves is the the misuse of affect, as in, "The affect of the forest fire is not fully known at this time." The proper word - in this context - is 'effect.' But I usually ignore it in the [green]Eng-Tips[/green] fora -



Please see FAQ731-376 by [blue]VPL[/blue] for tips on how to make the best use of Eng-Tips Fora.

 

[IDS]

A bit of wheel re-invention going on here I think.

Reinforced Earth dump structures with steel facing are common in Australia, and have been built to heights approaching 40 metres. They normally use semi-elliptical facing sheets formed out of 2.5 mm thick steel (usually galvanised) and steel soil reinforcement.

I'd recommend contacting Reinforced Earth in Sydney, they'll give you a quote for design, supply of materials, and construction advice.

A 15 m wall with dump truck loading is not something to be undertaken lightly - go with the experts.

Please e-mail if you would like contact details for Reinforced Earth, or if you'd like to discuss options further.

ps I was a Reinfrorced Earth employee until 3 years ago, so may be a bit biased

Doug Jenkins
Interactive Design Services

http://www.interactiveds.com.au

dougjenkins@interactiveds.com.au

 

[deckard452]

Thanks IDS,

This is the system I proposed. However I am not qualified to design such a structure - AS4100 (Australian steel code)would not be valid - and my recommendation was to use a specialist design service as you suggest .

The client is apparantly unimpressed with the typical steel faced reinforced earth walls you mentioned. He has cited a number of failures but I am not aware of the details. He also has other issues with the approach but I don't want to give a public airing to something I disagree with so I won't list them here.

My boss, who seems to side with the client, has responded to my serious concerns by assigning the task to a colleague who is not so concerned. I shudder to think of the possible outcomes but at least I am back doing something I am happy with.

I won't list my address here as it may identify the client and the actual project, but I'll be in touch with IDS soon

 

[Focht3]

[blue]deckard452[/blue]:

Do yourself a favor - document your concerns by recording what has already occurred. I had something similar happen to me about 17 years ago, and I did not document what happened. In the end, I was blamed for the fiasco! (That's the last stage of managing a project - "Blame the uninvolved.&quot At the very least, you may create the basis for a very useful technical paper -



Please see FAQ731-376 by [blue]VPL[/blue] for tips on how to make the best use of Eng-Tips Fora.