auger refusal standard 1

[Chewi00]

Is there a standard for definition of auger refusal on rock when drilling? I have language in a workplan that states soil stabilization will occur to bedrock (known elevation) or auger refusal....the state came back wanting to define auger refusal. I seem to recall 6 inches in 15 minutes from my fieldwork but have no reference for that.

Thanks in Advance
AChwalibog

 

[BigHarvey]

If things were so simple. The penetration speed depends on the torque and pull down force applied . Obviously refusal will be observed earlier with 10 tons.meters and O pull-down than with 25 ton.meters and 30t pull-down.
The shape and teeth of the auger will also influence the refusal.

Just to say that there is no standard for that !

 

[Panars]

My concern would be the equipment that is used to determine auger refusal. Auger refusal for a exploratory drill rig is very different than auger refusal for a drilled shaft (caisson) rig. In my experience, the geotech engineer is usually thinking of the former, but the contractor makes a changed condition claim on the latter.

 

[fattdad]

Boring logs should state the type of drilling tools and the type of rig (i.e., 2-1/4 HSA and CME 55). Auger refusal with a CME 55 and 2-1/4 HSA (hollow-stem augers) would be different than with a CME 55 and 3-1/4 HSA.

One thing to consider: If the driller says it's auger refusal, it's auger refusal! If you were to say, "Nah, try some more" and something broke, you'd likely be on the hook for the repair. Let the driller do his/her job and use the data accordingly. Just make sure that your drilling inspector makes appropriate notes and documents the field conditions at the time of auger refusal. You do have a field inspector, eh?

f-d

¡papá gordo ain’t no madre flaca!

 

[BigH]

Panars - good point on the clarification of rig (exploratory vs drilled shaft)!! Also, a lot depends on the type of rock. You might get shale bedrock that an auger - even an exploratory one (CME 55 or CME75) can penetrate 3 to 5 m or even more - it is rock - no question but . . . - this might be far below your "rock level". Good point, also on the "hook" for repairs. Might want to say it is rock refusal when there is "grinding" with no noticeable penetration and a "rise" in the kelly bar. Added pressure pushes up that which is trying to push down but can't overcome. Leave it at that.

 

[Chewi00]

THanks for the input...I also have said numerous times that there is so many variables that the on-site engineer with the driller would make a field call as to refusal.....ive never had to define it in a workplan.

 

[oldestguy]

Sounds like and inexperienced state person asking.

On that basis, be very simple. Maybe something like "When no significant advance of the rotating drill bit occurs".