should we considered passive soil pressure as well when we use springs to model the soil?

[Ehsan Ben]

Hi all,

I am working on a shoring system project modeling both in sap2000 and plaxis3d. in sap2000, I used line springs to simulate the soil for the embedded pile which is confined by the soil around it. I want to know should consider the soil passive pressure for the same part that has springs or not. in my opinion, having both springs and passive soil pressure means considering the soil effect twice and it is not correct.

Please refer to the simple figure I attached to this message. my questions are:
1- should I consider the passive pressure (blue pressure on the right side) when I have springs through the line of the concrete pile?
2- the active pressure should come to the lowest level (include the blue active pressure on the left side) or the black active soil pressure is enough. if it is the only black soil active pressure, please let me know why.

Thanks,
Ehsan

 

[DaveAtkins]

The springs will give you reactions, which you compare to the passive resistance available. You need to use a factor of safety against passive resistance.

DaveAtkins

 

[Ehsan Ben]

Thanks, Dave for your response. I don't think in SAP2000 we will be able to read the forces of line springs.
Since the springs work against the movement/displacements, they work similarly to the passive soil. That's why I say if we use springs then we should not add passive pressure. Otherwise, we are considering the effect of the passive soil twice.