Pile near a deep excavation

[chekre]

I have a building which has already been constructed supported on piles and a mat foundation. The bottom of the raft is -1.9.
A watertank has been added recently. It is composed of one basement, ground and a roof.
The bottom of its raft is -6.4.
I would like to know what is the minimum distance between the pile of the adjacent buildimg and the newly excavation to respect in order not to disturb the confined soil by the pile ?
Thank you.

 

[SlideRuleEra]

Are the elevations given in feet or meters?
How long are the existing piles?
What material, wood, concrete, steel H-pile, etc?
What is the existing pile spacing, center-to-center?
What is the existing pile size (diameter)?
Are the existing piles point bearing or friction?
Will the new piles be the same material and size as the existing?
Bottom of the new raft is -6.4. Is that the bottom of the excavation, too? Or will there be backfill up to -6.4?

http://www.SlideRuleEra.net

http://www.VacuumTubeEra.net

 

[chekre]

Elevations in meters
The piles are 15 m.deep
Concrete pile @ 2.5m spacing (80cm diamater)
Friction piles
There will be no new piles.
Watertank is founded on a mat foundation but i dont want to disturb the soil near the piles so i am asking abou the minimum distance between the pile and any excavation which will occur.
Is there any reference ?

 

[SlideRuleEra]

I would say the minimum distance is equal to the pile spacing, 2.5 meters. What I mean by minimum is that, IMHO, a properly braced excavation should be no closer than 2.5 meters. This is regardless of how "good" the soil may be. Consult a geotech engineer, they may recommend a larger distance than 2.5 meters.

http://www.SlideRuleEra.net

http://www.VacuumTubeEra.net

 

[oldestguy]

This is a potential block failure, taking the whole system toward the excavation. There was one of these on the Internet over in
China and a building came down. It requires a detailed geotech study, no cook book determination.