Drilled shaft (caisson) geotechnical inspection

[demha28]

Anyone know the standard practice for confirming the bearing surface for a caisson installation. The general construction notes is that a geotechnical engineer should be confirming that bearing surface for the caisson is competent. I suppose my question is that if the bearing surface for the caisson is designed to be on a dense silt / sandy silt dilatant material, how can a geotech confirm this stratum.

 

[JAE]

In my experience the local inspector would examine the tailings coming out of the hole at the end to verify it is the type of material recommended in the geotechnical report for bearing. Also they would visually inspect the bottom of the hole - using lighting from above - to verify a "clean" hole. Typically they wouldn't go down in the hole (I think OSHA frowns on that).

See also: https://www.eng-tips.com/threads/drilled-piers-inspection.266468/

 

[dik]

It's been decades since I've done a multi-storey building using caissions. At the time it was required that the shaft be greater than 30" dia and lined with a steel lining for anyone to enter. They went down in the 'bucket' used to remove soil and had a safety line.

 

[MTSOE]

FHWA has some good publications online discussing drilled shaft inspection. I would have a read through those. You could also consult the website of companies like Pile Dynamics.

 

[ANE91]

Fly a drone down into the hole. Land it on the bottom. Wait. Fly it up. Check the soil that stuck to it. Boom, you’re done.

 

[LittleWheels]

We tend to lower a 360 degree camera for a visual inspection with a small scoop fixed below it to collect a sample.