Question
I have started to build a retaining wall and the highest part will be about 6' high.  It is now only about 4' high and now I am concerned about the possibly of the wall falling over and killing someone.  We secured the RR ties together with 12" rebar staggering each one.  My question is, is there a way to secure the ties into the embankment to keep from possibly falling over? If so, what and how should we do it.  I have some ideas, but would like a professional opinion. If you do not have an answer, could you pass this question on to someone who may have a solution!
Thank you.

Answer
Hello,

This is why a do it yourselfer should never construct a retaining wall over 4 feet high. Any wall over 4 feet high is subject to forces that must be addressed by an engineer. I cannot give advice on any wall over 4 feet high.   If you want a retaining wall 6 feet high you must have it designed by an engineer and built by a qualified contractor.   Building retaining walls over 4 feet high is very dangerous,as evidenced by the fact that you are afraid it might fall over and kill someone and it just might.  I do not know what your training is,but engineering students with knowledge of engineering have been injured and killed with structures they designed,so have this retaining wall designed by a licensed engineer if you are going to 6 feet.

Railroad ties are not a good choice for a retaining wall.   If possible,go with a stronger and more durable  material like poured concrete or concrete segmental retaining wall blocks.   This material is heavy and forms a "gravity wall",that holds the soil back by the weight of the wall.  In addition there are various anchoring schemes and cantilever walls that give greater holding capacity to the wall.   Segmental blocks fit together by key and groove,can be staggered and can be held together by metal pins.   Railroad ties would have to be anchored back with "deadmen" to be effective.    The absence of deadmen anchors is probably why your wall is not secure.   Railroad ties are just too light to act as a gravity wall.   Sloping the railroad ties back at an angle would also improve their holding capacity.

The tiebacks,which are sometimes referred to as "deadmen" (actually the deadmen are weights that anchor the ties in the soil behind the retaining wall, but sometimes the ties and anchors together are called deadmen) can be steel cables,treated timber or reinforced geotextile mesh.   The geotextile is a sheet running the length of the wall horizontally,sometimes anchored by steel cable and concrete weights.  The rule with cable is one cable for every 16 square feet of wall.   Place the cable through the face of the railroad tie and back to the deadman,which would be a concrete block a minimum of 1 foot square.

The ties must go beyond the fill area behind the wall a minimum of 2 feet.  They must go back to undisturbed soil.   Keep the cables at least 12 to 18 inches below the surface of the ground on the top of the retaining wall.

Staggering the railroad ties does not sound like a good idea.  Try to tie them stacked.  Use as long a bar as possible to go through each course of ties.   While a railroad tie wall of over 4 feet would still employ the same building principles,the forces acting on the wall will change and will require the services of an engineer.   Good luck.  Write back if you have further questions.

Mark  Harshman
http://www.mahdrafting.com
Email: [email protected]

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