Shelby tubes smaller than 3 in diameter 3

[pelelo]

Engineers,

As you may know, the most common shelby tube diameter is 3 inches.

There are 2 inches diameter shelby tubes available as well. I was wondering what are they useful for?.

It is my understanding that for consolation and triaxial testing, it is required 3 in diameter, however I am not sure what 2" will be used for.

Please let me know,.

 

[TigerGuy]

We used some smaller ones, maybe 2 inch, when advancing borings with a Geoprobe rig. If the soils are exclusively fine-grained, you can still run triaxial tests on the sample. Remember, many labs shave the Shelby tube samples down to 1.4 inch diameter for permeability and shear testing. If they extrude the samples soon enough, it should provide high quality results.

 

[GeoEnvGuy]

When doing mud rotary drilling with casing with an ID between 3 and 4". You are forced to use the 2.5" or 2" Shelby tubes. As mentioned above, most of my advanced testing oedometer and DSS, shaves the samples down.

 

[pelelo]

Thanks,

What about for Triaxial testing?, a 2-inch sample diameter will be enough?,

Please let me know.

 

[TigerGuy]

As I stated, if there's no gravel in the soil matrix, most labs trim the sample to 1.4 inch diameter. This reduces the time to saturate/consolidate the sample or whatever hydraulic prep is needed before shearing.

 

[pelelo]

Thanks Tigerguy.

 

[BigH]

We typically used 51 mm tubes for our projects in clays in Ontario. Question? - are you using "real" thin walled shelby tubes (meeting all the dimensional specifications as per ASTM D1587) or thin walled steel tubes?

from Terzaghi Peck and Mesri

 

[pelelo]

Thanks BigH,

I have been doing some research between the drilling supply companies. what they sell are 2-in OD shelby tubes.

Do you know who sells "real" thin walled shelby tubes in USA?

 

[TigerGuy]

I think I used to order them from Boart Longyear. Humboldt Manufacturing may also have them.

 

[geotechguy1]

I'm sure that I also saw primarily 2" OD tubes being used in Alberta, Canada