Fellenius and 'Locked in Load' on Piles

[dmoler]

I have trouble understanding Fellenius's concept of a 'locked in load' during the pile installation process. I have read numerous papers from him about this, especially those emphasizing that measurements from strain gauges before pile installation must be incorporated into the analysis of load transfer and strain gauge measurements during load testing. I cant seem to 'get it' though. Also, nobody incorporates this that I know, and it seems to go against the great Terzaghi's method somewhat. Any comments or enlightenment on this is greatly appreciated.

 

[BigH]

I'll try to look into this. Fellenius is pretty damn good and he is one engineer who makes his stuff available - he is a panelist for DFI questions, geoforum, etc. But, there are times he goes against conventional ways. You might want to check out his eBook. I think it costs $10. Pretty cheap. It'll be a bit later, but I'll try to get back to you.

 

[SlideRuleEra]

Perhaps you could call or email him. Here is a link to his web site

http://www.fellenius.net/

http://www.SlideRuleEra.net

 

[dmoler]

Thanks for the insight, SlideRuleEra.

Anyway, Let me elaborate some on this, since it actually appears somewhat of great magnitude.

I use strain gauges alot in load tests since many tall buildings like to have a parking garage attached to them, and the parking garage usually has shorter piles. Using strain gauges allows me to determine the load transfer for the shorter piles for the parking garage and at the same time determine some aspects of the load transfer for the taller building in one load test, but not much really useful data for the taller building (left for another topic).

Consequently I have some correlations built up with a large database for the sand and limestone shear strength vs. SPT data and coring compressive tests, all acquired with strain gauges via load testing. However, I never did take the 'zero' reading before the strain gauges were put in the augercast pile, and subsequently according to him I might have a 20% error! in my data.

Now, this is actually somewhat magnified in importance, since all load data by my old professor from UT Austin, Prof. Reese, used strain gauge data for his evaluations after the piers/piles were installed. So, this may be of somewhat importance for those of us who use the Beta method, and for weak rock.