- #1
miloziz
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How can I verify the depth and size of existing caissons(assumed 100' deep) under 6 feet of concrete slab
Verify the depth and size of existing caissons
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Discussion Overview
The discussion revolves around methods to verify the depth and size of existing caissons, which are assumed to be 100 feet deep and located beneath a 6-foot concrete slab. Participants explore various techniques and considerations related to this verification process.
Discussion Character
- Exploratory
- Technical explanation
- Debate/contested
Main Points Raised
- One participant suggests drilling through the cap of the caisson and using a specific laser scanning system for verification.
- Another participant agrees with the drilling approach and mentions the possibility of using low-frequency acoustics, similar to methods used in the oil industry for well-logging.
- Questions are raised about the original drawings of the caissons and the materials used in their construction, such as whether they are made of wooden or steel cribs and if they were backfilled.
- A participant notes the significant depth of 100 feet plus the 6-foot concrete slab, indicating that finding the original drawings or using acoustic methods may be necessary for verification.
Areas of Agreement / Disagreement
Participants express various methods for verifying the caissons, but there is no consensus on the best approach. Multiple competing views on techniques remain, and the discussion is unresolved regarding the most effective method.
Contextual Notes
Limitations include the assumption of the caisson depth and the potential challenges of using ground-penetrating radar (GPR) due to its limited penetration depth for the specified 100 feet.
- #2
mgb_phys
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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!)
(Disclaimer - I build them!)
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- #3
berkeman
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mgb_phys said:
Very cool machines, mgb!
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- #4
Astronuc
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That's pretty much it - either bore through it, or excavate or bore through the ground beside it.mgb_phys said:
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?
- #5
mgb_phys
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berkeman said: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.)
- #6
FredGarvin
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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.
- #7
miloziz
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thanks
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