Basic MSE Wall Question

[bhert]

Greetings,

I just had a simple question that I was hoping to get an answer to. I'm in a situation where I am required to excavate 20ft below an at-grade railroad bridge with an ~8 lane road totalling 144 feet in width. I will need to build some sort of retaining structure to hold this soil back. I know that MSE walls are not desirable in cut situations, but boring tests have shown that the soil being excavated is suitable fill material for MSE Wall. In this case, would it still be feasible to construct an MSE wall in this location, or should I stick to somnething like a retaining wall? Thanks for any help.

 

[FixedEarth]

Stick with a cantilever wall supported by piers. The railroad surcharge, active earth pressure and associated higher bending moment (tall wall) may guide you to this choice. May likely require two rows of drilled piers or piles.

 

[Riggly]

This is not very clear as to where you are going to excavate with respect to the bridge. How far from the bridge will you be excavating. What type of foundation is supporting the bridge? Is the excavation along the bridge? If so how long? What is the purpose of the excavation?
Anyway,typically if you are going to excavate that deep close to a structure, you will need a support system in place prior to excavation. A cantilever wall can only be constructed after excavation is performed. A solder-pile with tie-back or, secant pile wall are all possible, but with limited data, it is difficult to make a better recommendation.