propped retaining wall close to spread footing
propped retaining wall close to spread footing
(OP)
Hi All,
The client wants to have an underground water tank on the first floor. This is a new RC framed building. The tank has four columns close to the four corners of the proposed tank (approx. 2-3' away from the footing edge). The column footing are typically 5x5 or 6X6' spread footing at 5' depth. The tank is approx. 10' deep. No drainage is proposed for the tank walls.
I am thinking of designing the wall as simple span, with at rest pressure with 0.5 times the vertical foundation pressure as surcharge. Also adding the hydrostatic pressure below water level. Is this the correct approach? Does it adversely affect the column footings (settlement??)?
Thanks in advance,
Sarju
The client wants to have an underground water tank on the first floor. This is a new RC framed building. The tank has four columns close to the four corners of the proposed tank (approx. 2-3' away from the footing edge). The column footing are typically 5x5 or 6X6' spread footing at 5' depth. The tank is approx. 10' deep. No drainage is proposed for the tank walls.
I am thinking of designing the wall as simple span, with at rest pressure with 0.5 times the vertical foundation pressure as surcharge. Also adding the hydrostatic pressure below water level. Is this the correct approach? Does it adversely affect the column footings (settlement??)?
Thanks in advance,
Sarju





RE: propped retaining wall close to spread footing
You probably know that the tank needs to be weighted or anchored to keep it from floating and pushing up the floor slab.
RE: propped retaining wall close to spread footing
GWT is very low according to construction in nearby areas. They'll construct the tank prior to the construction of footings. Braced excavation seems likely.
RE: propped retaining wall close to spread footing
RE: propped retaining wall close to spread footing
I thought the building was already in place. If you can build the tank first, your approach looks OK. You can be a little more conservative with the wall design without spending a lot of money. But if you build the tank in an open excavation with sloped sides, backfill will be necessary. I would avoid supporting the footings on the backfill unless you have great faith in the contractor and the inspecting agency. It would be best to avoid the risk and build the footings at the basement level as Hokie66 suggested.