Railroad Rail Retaining walls 2

I have been contacted by a local government regarding installation of a railroad rail retaining wall to correct a slope failure along a roadway. Is anyone aware of any design or construction guidelines which might be available.

Thanks

 

[Ginger]

It depends how you want to construct the retaining wall. The fact that it is adjacent to the railway is not particularly relevant unless this generates physical wall construction retstraints. The railway will simply add a surcharge effect and possibly vibratory effects to the loading condition for the wall.

For a sheet piled design you could use The Piling Handbook Method - issued by CORUS, or the CIRIA 104 method if you are bedding into stiff clays.

Other options such as secant piled walls and in-situ/precast concrete retaining walls can be designed to British Standard BS8002-Code Of Practice For Earth Retaining Structures; or BS 8006 -Code Of Practice for Strengthened/Reinforced Soils if you want to nail or reinforce the embankment. Andy Machon

 

[austim]

Thebenz,

Do you mean that your wall is to be made of old rails? If yes, then design it just as you would design a sheet piled wall.

 

[Ginger]

My apologies. I misread your question. If you are proposing to use steel rails as retaining wall members then this does not seem very efficient. The rails are not very wide and you will need a lot of them!!!! But, in theory then, yes, you could use them like sheet piles but they will take some driving in.

The other way is to use the rails as King Posts installed vertically every 2m or so. You then board in-between the rails with timber boards called "laggings". The design of such walls is covered by CIRIA report SP95 - The Design and Construction of Sheet Piled Cofferdams. Andy Machon

 

[boo1]

Retaining wall design and wall type selection is driven by several factors. These factors include cost, required wall height, ease and speed of construction, ground water conditions and soil characteristics.

Designing any retaining wall requires a knowledge of lateral earth pressure, the pressure developed by the backfill. It is the force generated by the lateral earth pressure that constitutes a large part of the load that the wall must carry. To determine the lateral earth pressure acting against the retaining wall, several soil parameters must be known in order for the qualified engineer to assess a particular wall design and its overall stability:

soil unit weight
angle of internal friction of the soil
cohesion and plasticity indices for cohesive soils (for instance, clays)
water table location.

Once the lateral earth pressures are known, the wall is checked for stability. This includes checks for wall overturning, base sliding, and soil bearing capacity failures. Improper wall design and installation results in failures of retaining walls.

By understanding how a wall works, and how it can fail, it is possible to engineer a retaining structure that will meet all foreseen environmental, structural and construction demands. But I recommend passing the design to a "Qualified Engineer".

 

[Focht3]

Boo1's comments are on target. But something about the proposed use of railroad rail suggests the wall is not very tall or significant. Or that the local government badly underestimates their problem and you may get stuck with the repair cost when your solution (using their materials) doesn't work.

First, a few questions. Where is your site? How long are the rails? What is the approximate section modulus? What are the approximate cross-section dimensions?

The importance of the wall is driven by several factors, such as wall height, what it retains, and the slope angle. If it is short (say, 1.5 meters or less), flat (less than 25 degrees from horizontal), nothing of significance is behind it and excessive wall movement will not impede roadway traffic, then the consequences of failure may be small. A "soldier pile and lagging" design (see Andy Machon's comments) in a moderately strong clay soil should work fine provided the rail penetrates the ground at least twice as far as its exposed height and fully penetrates the slope failure enough to reinforce the slope and prevent further movement. (That's a big "provided".) I wouldn't exceed a rail spacing of 2 meters; and a rail spacing of less than 1 meter may be required depending on ground conditions, backfill material and the problem's geometry.

If the wall height exceeds 1.5 meters, will be located where the public will walk or drive along it (and notice it is leaning), or will retain soil adjacent to a building or public space that cannot tolerate horizontal/vertical movements that could exceed 80 mm (3 inches), or potentially cause damage to a third party (like an adjacent property owner), pass this assignment to an experienced engineer.

A note of caution: you did not indicate the total height of the slope that this wall will be repairing. (This may be - and probably is - different that the wall's height.) Slope failures generate very large forces. If the total slope height exceeds about 2 meters, or is steeper than 3:1 (H:V), then used rail may not be appropriate.

Keep in mind that the existing failure may become YOUR failure if you aren't careful.

 

[DRC1]

For retaining walls along Railraods you need to consider the railroad loading. Usually the railroad will give a "Cooper Loading", Which is 2 steam locomotives and 2 coal tenders. Typically an E-80 loading is used. A diagram of the loading is given in the AREA handbook. I take the load and divide bythe length of the locomotives and tenders times the width of the ties, which is about 8 feet, to get a unit contact stress. I use this as a surchage stress for the wall design. For an E-80 load the stess is about 1200 psf and the length of the locomotives and tenders are 120 ft long, but you should run your own numbers.
Good luck

 

[Rockjoint]

Thebenz,

Did you complete the project concerning the use of railroad rails? I am interested, as I am working on a project doing just that, for a highway slope failure. This concept has been utilized very successfully in the state of Kentucky (USA). I am working in Tennessee (USA) and am quite optimistic about this remediation/mitigation method. I will provide details under separate email if desired.


Rockjoint
rockjoint@yahoo.com

 

[PEinc]

Rockjoint,

In the previous posts, no one ever indicated where the slope's failure plane was located. Was the failure confined only to the sloped face or is there a deep-seated failure where the failure surface extends below the base of the slope? If there is a deep-seated failure surface, a cantilevered (sheeting) retaining wall, especially a railroad rail soldier beam wall, will be inefficient or unsuccessful in holding the slope. Thebenz may have needed a more substantial wall with tieback anchors. You may need the same for your project.

I would think that a soil investigation and testing program and a subsequent slope stability analysis are in order before jabbing railroad rails into the ground.

Also, even if the retaining wall is relatively short, are rails the best structural member to use? Probably not. As Ginger mentioned above, rails are narrow and inefficient. They also may not be readily available. Railroad rail walls are economical only if you already own the rails and the wall height is minimal. In my opinion, railroad rail walls are for inexperienced, do-it-yourselfers with insufficient funds to build a real wall.

Just because Thebenz discussed using railroad rails, it does not necessarily mean that his wall would be supporting a track surcharge. Search previous threads for discussions on Cooper E80 railroad loading. Also, your highway wall may need to be designed to AASHTO specifications. If a railroad is involved, you may also need to follow the specifications of AREMA (formerly AREA) and the particular railroad involved.

 

[Focht3]

Well said, [blue]PEinc[/blue]. I agree entirely.

"TheBenz" posted as a visitor (which is no longer allowed) and may not return. This thread probably should be closed -



Please see FAQ731-376 for great suggestions on how to make the best use of Eng-Tips Fora. See faq158-922 for recommendations regarding the question, "How Do You Evaluate Fill Settlement Beneath Structures?"

 

[Rockjoint]

Thank you PEinc and Focht3 for your comments, all of which were well taken. As a relatively inexperienced geotechnical professional, I value your opinions and experiences. Thanks for all your other posts, as well.


Rockjoint
rockjoint@yahoo.com