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Adhesion Factor in Pile Design

Adhesion Factor in Pile Design

Adhesion Factor in Pile Design

(OP)
Hi to All,
There is a site the soil texture of which is unsaturated hard clay. Bored-and-cast-in-place concrete piles are designed for heavy loads. At the same time the risk against saturation of the site is being taken into consideration by designing the same pile type using the undrained shear strength values gained by performing tests on  the laboratory saturated (and some remolded) samples.
I appreciate it if I receive some comments on:

1- The adhesion factor to be imposed on the saturated undrained shear strength (The strength value which does not actually exist at site now).
 In my opinion this factor could not necessarily be the same as what has been presented in the related references (say “Pile Design and Construction Practice” by M.J. Tomlinson). The point is that, it is the unsaturated cohesion which is affected by boring method and if needed, the bentonite slurry etc., rather than the saturated value.

2- Is there any practical way to investigate the predicted bearing capacity values in the saturated condition by an axial pile loading test? Say any case histories or…?

Regards

RE: Adhesion Factor in Pile Design

You may wish to refer to paper by Dan Brown- Effect of Construction on Axial Capacity of Drilled Foundations in Piedmont Soils - Journal of Geotech and Geoenviron Engineering, December 2002. You may wish to look also at effective stress parameters to determine frictional resistance. 2 mm of movement is required to engage frictional resistance.

Suggestion- Use shear strength between saturated and remoulded test at 2 mm movement to assess undrained shear strength. Compare this with shear strength of in place soil. Develop some factor and compare with those in Tomlinson's text- you should be able to come up with some answer using this geo-magic. Keep playing with the numbers and using your wand.

Regards  

RE: Adhesion Factor in Pile Design

The Corps of Engineers Engineering Manual No. 1110-2-2906 Design of Pile Foundations has a small section on this.  You might download it from their site.

Best Tincan.

RE: Adhesion Factor in Pile Design

(OP)
Thanks all
Regards
cmorgh

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