Retaining wall replacement

[StrucPatholgst]

I have a client who has a retaining wall at the edge of a parking lot. At it's max height, the wall is only 2 feet high, constructed of stacking unit blocks with pins (reportedly). The on-site maintenance supervisor reported off-handedly that the original wall was a timber wall with dead men. When I asked him further about it, he said when the top course of the timber wall started to rot, they installed a stacking unit wall about 2-3 feet out from the timber wall, and laid in two layers of geotech fabric and gravel in the void between the old and new walls. He said they left the timber wall in place (except the top timber which they pulled out) because they didn't want have to redo the sidewalk if they pulled the deadmen out wrong (which apparently lie beneath the sidewalk). Work was done in 2010. I can't visually see anything wrong with the installation. No low spots, etc. Anyone ever hear of leaving a timber wall in place and installing a stacking unit wall in front of it?

 

[SlideRuleEra]

I did virtually the same thing 7 years ago for a residential retaining wall, about 60' long, that varied in height from zero inches to 44", then back to zero inches. The top of the wall is level, the ground elevation at the base of the wall varies. Where the wall is 44" high, there is a mature tree about 2 feet behind the existing timber wall (horizontal railroad ties). The tree would have been destroyed if the timber wall was removed. Constructed a new gravity block (concrete) wall about 18" in front of the existing timber wall. The new wall is about 2" higher than the old wall. As the block wall was erected, filled the space between the two walls with compacted soil, no geotextile fabric. To date, no settlement or loss of soil. No block shifting or movement noted. The tree continues to thrive.

http://www.SlideRuleEra.net

http://www.VacuumTubeEra.net

 

[Terratek]

The only concern I can see would be possible settlement after decomposition of the buried timbers. That would really only be an issue if there was flatwork or pavement supported above the timber.