Verify the depth and size of existing caissons

[miloziz]

How can I verify the depth and size of existing caissons(assumed 100' deep) under 6 feet of concrete slab

 

[mgb_phys]

Drill through the cap and use something like this http://www.mdl.co.uk/laser_systems/cavity-autoscanning-laser-system-c-als-/index.html
(Disclaimer - I build them!)

 

[berkeman]

Drill through the cap and use something like this http://www.mdl.co.uk/laser_systems/cavity-autoscanning-laser-system-c-als-/index.html
(Disclaimer - I build them!)

Very cool machines, mgb!

 

[Astronuc]

Drill through the cap . . .

That's pretty much it - either bore through it, or excavate or bore through the ground beside it.

One could possibly use low frequency acoustics - le.g. seismic analysis - used in the oil industry for well-logging and characterization of subsurface strata.

GPR doesn't penetrate far enough for 100'.

Can one find the original drawings?

Are the caissons constructed of wooden or steel cribs under the concrete cap? Were the caissons backfilled?

 

[mgb_phys]

Very cool machines, mgb!

Thanks - it's a clever application of a very simple idea.
Hope nobody minds the advertising! (I only work for the company - I don't own it.)

 

[FredGarvin]

100' is a long way down plus the 6' of concrete slab on top of it (that is one seriously thick pour!). I agree with Astronuc that the acoustic route may be your only bet short of finding the original drawings or pulling one out of the ground.

 

[miloziz]

thanks