dark brown dark gray decompossed WOOD

[AnastasiaKa]

Dear geos,

I would appreciate your opinion. I am currently busy with a pile foundation (steel open tubular piles) and I am reading on the bor logs, "dark brown, dark gray decompossed WOOD" with a SPT values of 20, 31 and 34. Thickness of the layer is 5.0m on a depth of -27.0m CD.

I was thiking of simulating it as a clay material on my API pile capacity curves but how correct that would be with respect to the shaft friction and end bearing? Same question for the p-y curves of such a layer.

Should it be recommended to go through the entire layer and found my pile on the sand layer beneath?

Thanks

 

[Ron]

In my opinion not accurate at all! This layer is significantly thick and will decompose even more with time. I would model as an organic silt with little or no shear strength. The SPT values mean nothing in this material.

Is there a possibility that perhaps the boring went down the trunk of an old tree. Do your other borings show the same layer?

 

[molerat2210]

Not similar to clay layer. Wood may rapidly decompose once exposed to air/oxygen. Extend piles through wood into sand bearing stratum. Consider downdrag due to compression of wood.

 

[fattdad]

expect no strength and the potential for downdrag of the overlying soils if the organic horizon is above the water table or if there are surface loads that would affect the stresses in the organic layer.

f-d

¡papá gordo ain’t no madre flaca!