Gabion bridge bulkhead

[samclane]

We are considering using a gabion basket bulkhead (9'h x 6'w x 21'l) to support a railcar bridge. Maximum truck load is 100 tons. Rock may not be available. Will gabion strength be compromised if they are lined with geotextile (reinforcement grade) then filled with gravel (1/4" to 2&quot?

 

[VAD]

Hello samclane:

Interesting idea. I raised this idea question on several occasions in the past. A couple of years ago I attended a Macaferri seminar and was tickled when a basket was shown with geotextile liner. So the question arose. Do you know that the chief users of the system is the military to create bulkheads in their training practice as the bakets can be filled with sand and can be readily removed as they are stacked up. In fact it was for this reason that Macaferri developed the idea.

Of course I asked if it was being used by Civil Engineers an the answer was no. I then discussed the same concept as you are enquiring about and thought it would be an excellent approach in areas of rock shortage. The way I looked at it was to create the outermost baskets with rock and the inner ones with gravel or sand. This way the outer baskets would be rigid enough to restrain the others from bulging due to more deformable materials. This would also reduce over costs

I think it is a great idea and should be pursued. One can even place a maix that had a small percentage of cement to promote grain to grain contact and afford some rigidity to th structure. All the gabions would be doing is to provide containment to the gravel. As you know if granular material is confined then the load carrying ability and performance improves dramatically. You can also stiffen baskets with rebar driven at the corner and centre etc. Lots of ideas can result based on the problem.

Others may have other opinions to present as well

Regards

 

[Focht3]

See my response to the same basic question in this thread:

thread255-86356

[blue]VAD[/blue]'s approach - with sand and crushed rock - is possible, assuming you have "enough" crushed rock in the outer baskets to help "lock" the mass together. But I wouldn't use a gravel for this purpose.



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[BigH]

Might I suggest you keep your posts to one thread rather than multiple ones? It will keep the flow going better.

 

[GabionGuy]

VAD,

The system you are referring to is Flexmac. I would not recommend it as being appropriate for use in this situation.

samclane,

There are a number of woven wire mesh MSE systems that may be appropriate for this application. The Terramesh System MSE structures have numerous facing options. You may want to contact Maccaferri about the Terrawall System. This system was specifically developed for use in locations where 100-200mm stone was not readily available.

 

[VAD]

Gabionguy:

Thanks for the reminder of the name. However, I fail to see why this system cannot work in the context discussed.

Regards

 

[Focht3]

You can't get enough shearing resistance from the gravel; you are really counting on the baskets - and ties - for strength. It isn't a good plan in my experience -



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[VAD]

The concept discussed was typical gabion rock in the baskets on the outside of the bulkhead i.e those on the slope side or span side or whatever. I can make this system work.

 

[Focht3]

The original post included the following:

We are considering using a gabion basket bulkhead (9'h x 6'w x 21'l) to support a railcar bridge. Maximum truck load is 100 tons.

This isn't a self-weight problem; stability through the embankment must be assured. You can't simply put a token amount of crushed rock in the outer baskets and expect the gabion embankment to remain stable with the majority of baskets filled with a river gravel -



Please see FAQ731-376 for great suggestions on how to make the best use of Eng-Tips Fora.

 

[VAD]

Focht3:

As I said before the concept can work in my opinion. I am not sure that river gravel was mentioned to fill the baskets. In any event, gabion rock used extensively is composed of river gravel or field rock as well and not necessarily filled with gravel obtained from crushing. Before debating this topic any further we should have a sketch on what is actually required in the field.

Spread footings resting on compacted gravel fill has been used successfully at highway abutments. The gravel in those cases formed the uppermost layer of an earthen approach fill. We have been taught that the strength of granular material increases with confinement and normal loads.

 

[canoeman]

I took a Macaferri seminar years ago and at that time asked a question about using recycled concrete as a filler material for the gabions. At that time I was told that it was not done because engineering standards had not been written applying to recycled concrete.
Have any standards been written to anyone’s knowledge regarding this inexpensive and readily available material, pertaining to substituting for crushed rock?

 

[Focht3]

Not that I have seen -



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[GabionGuy]

canoeman,

Recycled concrete, crushed to 100mm-200mm size, has been used on occasion for gabion structures, but there are a number of issues that must be dealt with.

1.) All stone used for gabion structures MUST be sound, durable stone, not prone to breakdown under climatic conditions. For northern climates, this means freeze thaw durability. Unless you can guarantee that all of the source concrete was air-entrained, this will be a major problem.

2.) The crushed concrete must be free of any and all reinforceing steel.

I have only ever encountered one aggregate supplier that was willing to guarantee their stockpile of crushed concrete was 100% AE and free of all steel. We did build a gabion retaining out of it.

I do not recommend it as a standard practice, but that is not to say that it cannot be done on a project specific basis. Aggregate QA/QC is critical.