Unconfined compressive strength of rock? 3

[Jean_Wong]

Good Day!

What is a good assumption for the value of qu of rocks?

 

[Guest262653]

3.141592653

 

[Guest262653]

or more

 

[GeoPaveTraffic]

The best option is to test the rock. Second best option is to ask your geotechnical engineer.

If you just want to guess, then you need all of the following information, just as a starting point.

Type of rock.
Quality of rock.
Degree of weathering.
Age of the rock.
Part of the world where the rock is located.

Mike Lambert

 

[oldestguy]

Also direction of bedding, if any.

 

[Ron]

As GPT noted, testing is the better option. I have tested sedimentary rock that I expected to fail at 4000 psi and it tested to about 8000 psi. This just shows that various formations can produce various results. Test it.

 

[Okiryu]

Check also your local design guidelines. It may be some presumptive values for your local rocks there.

 

[fattdad]

Unconfined compressive strength testing of rock provides the intact rock property. In design, you'll need the strength of the rock mass. There are tables that provide some insight to the unconfined compressive strength of intact rock types - i.e., granite, marble, claystone, shale, etc. They'll vary by a wide margin.

The influence of discontinuities, water pressure, inclination of load, etc. all temper the intact rock properties.

Hate to give you advice that leads to ruin. The geologic structure will overshadow the strength of the rock mass.

f-d

ípapß gordo ainÆt no madre flaca!

 

[Okiryu]

f-d, your post reminded me that Das book recommends to use 1/5 of the unconfined compressive strength for calculating pile capacities in rock, for the reasons you and others have stated above.

 

[Jean_Wong]

Thanks for the info!

Some boring logs did not include qu of rock. The geotechnical engineer recommended the nearest boring log with qu values.