Passive pressure exceeds the active one
Passive pressure exceeds the active one
(OP)
Hello,
I am considering a retaining wall having a 3.5m height of retained soil and 1.7 meters at the base from the other side. I want to rely on my passive earth pressure. As per my calculations, the passive earth pressure induced moment exceeds the moment coming from the active.
In this case, how can I represent the real actions on the wall ? Can the active and passive earth pressures be developed as represented?
Thank you for the help
I am considering a retaining wall having a 3.5m height of retained soil and 1.7 meters at the base from the other side. I want to rely on my passive earth pressure. As per my calculations, the passive earth pressure induced moment exceeds the moment coming from the active.
In this case, how can I represent the real actions on the wall ? Can the active and passive earth pressures be developed as represented?
Thank you for the help





RE: Passive pressure exceeds the active one
RE: Passive pressure exceeds the active one
www.PeirceEngineering.com
RE: Passive pressure exceeds the active one
RE: Passive pressure exceeds the active one
www.PeirceEngineering.com
RE: Passive pressure exceeds the active one
1. When a very heavy load acts on the active side like a vehicle or building.
2. When the water level behind the wall rises and pressure is not allowed to be reduced due to clogged weepholes.
3. An unplanned cut on the passive side below the base of the wall hence reducing the available passive resistance.
When designing a cantilever retaining wall, it is not always good to rely too much on passive resistance provided by the soil in front of the wall. Try to use a longer heel or provide a key instead at the base.
RE: Passive pressure exceeds the active one
There are three states of earth pressure; at rest, active and passive.
For either active or passive pressure to be mobilized (realized) wall movement has to occur. It really doesn't matter how much movement occurs, just that it does occur. So, by definition, if the wall moves (bends, slides, etc.), the force causing that movement is the active pressure (it is "acting" on the wall to cause the movement). Think of the passive pressure as being somewhat like a bearing capacity of soil if you are putting a footing on it.....if you don't put a footing on there and load the soil (thereby causing movement, however slight it might be), the bearing capacity is irrelevant. The passive pressure, as PEinc noted, is then a reaction, just like the bearing capacity reacts the footing load below its failure point.
RE: Passive pressure exceeds the active one
To answer your above question, you need to check overturning and sliding, and depending on the code in your area, using either: 1) code-specified load factors applied to your actions, or 2) using working/service loads and calculate the F of S with say a minimum of 1.5 for overturning, for example.
In your calculations you appear to be using service level actions, and for overturning you do NOT appear to have a F of S of > 1.5.
You need to check sliding, bearing capacity...
RE: Passive pressure exceeds the active one
You are right. The main purpose of my thread was to discuss the passive earth pressure. But surely sliding and bearing capacity will be checked.
Regarding the safety factor of overturning and according to the above discussion the wall will move due to the active pressure and the passive will be mobilized. And since the passive counts as a resisting moment so the overturning is ok. (Please correct me if I am wrong and thank you for the help).
RE: Passive pressure exceeds the active one
www.PeirceEngineering.com