Retaining wall backfill
Retaining wall backfill
(OP)
I'm in the process of getting a retaining wall poured. How long will I have to wait to have the contraction performed backfilling? And at what minimum % strength should the wall be at that the time of backfilling?






RE: Retaining wall backfill
Mike McCann
MMC Engineering
Motto: KISS
Motivation: Don't ask
RE: Retaining wall backfill
RE: Retaining wall backfill
RE: Retaining wall backfill
RE: Retaining wall backfill
RE: Retaining wall backfill
RE: Retaining wall backfill
RE: Retaining wall backfill
Contrary to MMC, I never put the minimum strength or time on plans or specs, instead put the responsibility on the contractor to not damage the wall during backfill. Our local standards require 100% of the design strength for retaining walls.
RE: Retaining wall backfill
RE: Retaining wall backfill
RE: Retaining wall backfill
RE: Retaining wall backfill
Construction sequencing I have put a note on the drawing which says that the blockwall is to remained propped until the slab over and blockwall have achieved design strength (I know the image is poor quality...It is a scan).
I have had a tough time with the contractor who looked at the note and says to me "What rating are the props?...What centres are the props at?...What anchors are required for the props?...If the props are at 1200 centres (metric), what timber support members are required to span between the props?".
I ended up saying that the props are required to be rated for 2.5tonne and 1200 centres with no timber members required to span between the props because the blockwall will have achieved sufficient strength to span horizontally prior to backfilling.
When a note says the wall is to be propped, should a rated load be given for the props and should a minimum design strength be given before backfilling the wall?
I have called up 20MPa grout (2900psi).
RE: Retaining wall backfill
Typically where I work, the temporary bracing, or props fall within the means and methods of construction, and would generally fall under the contractors responsibility. Therefore the contractor should hire his own engineer to determine the required load rating, spacing, etc.
I would indicate such, and if he wanted to could hire you to design the temporary bracing system as an additional service.
RE: Retaining wall backfill
I often get the propping issue you are referring to and normally palm it off similar to mmillerpe - with varying levels of success. In your instance you need far less than the 28day strength of the slab for it to function as a prop. If damage was to occur to the wall it would have happened during the cantilever/& backfilling stage (assume they did prop it for this). In this situation i prefer to design these types of walls as partial cantilevers (enough to take the earth pressure only) ie make your starters longer and place them on the 'earth side'. This provides a more robust design (though i still keep all the notes).
RE: Retaining wall backfill