Pile Capacity on RQD Classification: Very Poor
Pile Capacity on RQD Classification: Very Poor
(OP)
I am designing a bridge, currently on the foundation part (Bored Pile).
The complete geotech report hasn't arrived yet, but they gave me advance copy of the borelogs that are already finished.
The classification is Rock, so no N values are given, only RQD, which ranges in Very Poor (5,15, 23% etc)
Now with only RQD as given data, how can I determine the appropriate or allowable bearing capacity on the bored piles? I have talk to someone over the phone, and he said that if the foundation is on rock, the only thing that we need to know is the "embedment length", since it is already on rocks. But I couldn't find any literature about that.
Any insights? Thanks in Advanced!! :)
The complete geotech report hasn't arrived yet, but they gave me advance copy of the borelogs that are already finished.
The classification is Rock, so no N values are given, only RQD, which ranges in Very Poor (5,15, 23% etc)
Now with only RQD as given data, how can I determine the appropriate or allowable bearing capacity on the bored piles? I have talk to someone over the phone, and he said that if the foundation is on rock, the only thing that we need to know is the "embedment length", since it is already on rocks. But I couldn't find any literature about that.
Any insights? Thanks in Advanced!! :)





RE: Pile Capacity on RQD Classification: Very Poor
Mike Lambert
RE: Pile Capacity on RQD Classification: Very Poor
Based on RQD values you can not design a deep foundation.
It is my understanding that at some point the designer will need to correlate or assume N values (in order to obtain friction angle). You can submit to a lab the rock cores and perform a direct shear test in order to obtain cohesion values. My opinion is RQD gives an idea of how strong or weak (or maybe how porous the rock is, if we are talking about limestone) BUT still, SPT-N values are necessary to perform more geotechcnical analysis.
That´s just my opinion.
RE: Pile Capacity on RQD Classification: Very Poor
www.PeirceEngineering.com
RE: Pile Capacity on RQD Classification: Very Poor
ftp://ftp.dot.state.pa.us/public/PubsForms/Publica...
See page 573 of 1177, Section 10.7.3.2 for piles driven to rock. There is also an AASHTO reference.
www.PeirceEngineering.com
RE: Pile Capacity on RQD Classification: Very Poor
Unfortunately the geotech report wasn't still with me.
As per our structural code, if the RQD is less than 25%, it is indicated to "Use qult for an equivalent soil mass". Can anyone elaborate? Thanks!
RE: Pile Capacity on RQD Classification: Very Poor
www.PeirceEngineering.com
RE: Pile Capacity on RQD Classification: Very Poor
RE: Pile Capacity on RQD Classification: Very Poor
www.PeirceEngineering.com
RE: Pile Capacity on RQD Classification: Very Poor
RE: Pile Capacity on RQD Classification: Very Poor
www.PeirceEngineering.com