Railroad Rail Piling for Embankment Failures 4

[Rockjoint]

Railroad rails have been used for years on highway embankment failures as a method of repair, with the rails functioning similarly to cantilever beams/piles. Rails have standard 39ft lengths and come in different weights: 130-133 lb/yd and 136-140 lb/yd.

Assuming proper embedment into rock or firm and stable soil, and all other parameters being the same, would there be a significant loss of factor of safety or other strength penalties with substituting 130-133 lb/yd rails for the heavier 136-140 lb/yd rails?


Rockjoint
rockjoint@yahoo.com

 

[BigH]

I'd doubt it - what you really are doing is installing pin piles. I would assume that the piles are driven quite close together with some driven straight - others driven at batters.

 

[PEinc]

Rockjoint,

The answer depends on what type of wall(?) you are building. If you are using the rails as soldier beams in a wall, the heavier rail may be slightly stronger than the lighter rail. You can calculate the section modulus for each rail section. However, both rails should be relatively weak as soldier beams in bending when compared with H Piles or Wide Flange Beams.

If you are using the rails as driven soil reinforcements, like pin piles as assumed by BigH, then I would think that both rails are relatively strong. However, the heavier rail should be a little stronger since it has a greater cross-sectional area to resist shear.

No clear answer can be given unless we know what you are trying to do with the rails.

 

[BigH]

Thought about that - but the weight difference is only 10%.

 

[jdmm]

There was a collapse of a mid-rise residential building in Kuala Lumpur many years ago that killed many people. The building was supported on used steel rails. The cause of the failure was attributed to a slope movement adjacent the building causing displacement of the piles.

Although I only read the paper, I was always concerned that the used rails may have become brittle as a result of work hardening and that the minor horizontal displacement of the slope resulted in catastrophic results.

Maybe someone can shed some light on this issue. Presumably the railways remove rails for some good reason. Is it simply wear or is there a change in the material property that might affect their use in the situations suggested here.

 

[Rockjoint]

As clarification, the "railroad rail" concept is limited to rather small sized embankment failures, like what we often see along our highways in mountainous areas (Eastern USA). Often the failures are less than 20 ft in height, but may run for several hundred feet.

In an effort to prevent closing of both lanes of traffic, especially in limited space areas, and where remediation with rock buttress material may impact streams, etc., this concept has been utilized on small failures.

The used railroad rails are placed into drilled holes, which are then backfilled with crushed stone or concrete. A portion of the rail is exposed above natural ground surface where lagging (often guardrail) can be placed against the rails. Crushed stone then may be placed against the lagging to bring the backfill up to shoulder grade. Note that the rails are 39 feet in length, limiting where this concept may be used.

We consider this remediation concept for shallow failures, especially where bedrock is located along the failure surface. In all cases over the last several years, the failures have been successfully stabilized.

I am a geologist, not an engineer. I work with the engineers, however, to recommend where such remedial measures may be considered. Of course, other methods such as tie-back walls and rock fill may be used.





Rockjoint
rockjoint@yahoo.com

 

[DRC1]

The properties of railroad ties are tabulated. Used as a cantilever beam, The rail will need to resist bending. The most important value is the section modulus (Sx). Note that because the rail is not symetrical about the axis of bending, you will have 2 Sx values (usually noted as S1&S2.)Also, because the lower flange is much thinner than the head of the rail buckling is a concern. Also need to know grade of steel. This really isn't as bad as it sounds. A good structural engineer can help you determine the capacity of the rail pretty quickly.
Good Luck!

 

[Rockjoint]

Thanks to all the professionals for your input. I do appreciate it.



Rockjoint
rockjoint@yahoo.com