Retaining Wall: Saturated Soil & Hydrostatic Pressure
Retaining Wall: Saturated Soil & Hydrostatic Pressure
(OP)
I understand that Hydrostatic pressure and Soil pressure exist cocurrently. I am curous if there are any additional variables at work when calcuating total pressure on a retaining wall.
Full disclaimer: I am not an engineer nor do I pretend to be one. I recognize that these are very basic questions, but I am at the early stages of my understaing. Please be assured I am not and will not attempt to engineer any actual structures.
Full disclaimer: I am not an engineer nor do I pretend to be one. I recognize that these are very basic questions, but I am at the early stages of my understaing. Please be assured I am not and will not attempt to engineer any actual structures.
- Does the pore size limit, in any way, the surface area available for hydrostatic loading on the back of a retaining wall? I assume it does not. It would stand to reason that water under pressure would suspend the soil particles and push its way to the point where most of the surface area on the back of the wall was under a hydrostatic load?
- Soil particules become suspended in water while a hydrostaic load is present. Does this (or any other water related factor) affect the overall soil load or does it remain the same?
- Is the total load on the wall simply (1/2 * H² * γ * Ka) + (1/2 * H² * 62.43) ? (Where γ = the soil density)?





RE: Retaining Wall: Saturated Soil & Hydrostatic Pressure
RE: Retaining Wall: Saturated Soil & Hydrostatic Pressure
The marbles analogy helps. I suppose I was thinking about liquefaction, which would only occur during an earthquake or similar event.
So, this goes back to water pressure; something I'm ashamed to admit I struggle to understand.
I keep imagining an L shaped PVC pipe, with the bottom of the L against the bottom of my wall (so it forms a seal). When it's fill to the top with water it would only be exerting a small force on the wall, equal the pressure times the surface area of the pipe opening.
For some reason I assumed the opening between our marbles would by analogous to many L shapes PVC pipes pressed against the wall. There would have gaps in our surface area where the marbles touch the wall.
This would exert a lot of pressure, but not the same amount as if the entire wall was in contact with a volume of water behind it.
I feel that this is wrong, and i'm struggling to figure out why. Any help correcting this picture would be much appreciated. I feel bad re-hashing such elementary subjects but I know if I don't have a firm grasp of the basics I wont be able to progress.
RE: Retaining Wall: Saturated Soil & Hydrostatic Pressure
RE: Retaining Wall: Saturated Soil & Hydrostatic Pressure
So if I had a 4 foot high retaining wall with a active soil pressure (Pa) of 830lbs per linear foot, and I also had a hydrostatic head 4ft high behind the wall this would give me an additional 500 lbs of added force:
4² ⋅ γw / 2 = 499.44 lbs per linear foot (where γw = cubic weight of water, 62.42 for this example )
This gives me a total of 830+500 = 1330lbs per linear foot of wall.
Is this correct? Is there anything I've misunderstood or didn't take into consideration?
(thanks again for your patience, I just want to make sure I understand this)
RE: Retaining Wall: Saturated Soil & Hydrostatic Pressure
RE: Retaining Wall: Saturated Soil & Hydrostatic Pressure
RE: Retaining Wall: Saturated Soil & Hydrostatic Pressure
Dik