geotech help.. skin friction, shear strength, compressive strength of drilled pier
geotech help.. skin friction, shear strength, compressive strength of drilled pier
(OP)
I have a 24" diameter x 15 feet drilled pier
I only have boring log with compressive strength of 820 psf, qu
this is where I need help if I'm using correct formula.
The objective is to get overall drilled pier capacity both skin friction + end bearing
Su = qu / 2 = 820/2 = 410psf
skin friction = alpha x Su / 2 = 0.6 x 410 / 2 = 123 psf
end bearing = 9Su/3 = 9*410/3 = 1230 psf
is my Su, SF, end bearing formula correct?
I only have boring log with compressive strength of 820 psf, qu
this is where I need help if I'm using correct formula.
The objective is to get overall drilled pier capacity both skin friction + end bearing
Su = qu / 2 = 820/2 = 410psf
skin friction = alpha x Su / 2 = 0.6 x 410 / 2 = 123 psf
end bearing = 9Su/3 = 9*410/3 = 1230 psf
is my Su, SF, end bearing formula correct?






RE: geotech help.. skin friction, shear strength, compressive strength of drilled pier
Whether your logic is correct is more than anyone here is going to be able to say based on what you have provided. You need to have an experienced geotechnical engineer look at the boring log, geology, proposed structure, allowable settlements, and a few dozen other generally less important details to be able to determine the allowable load for a drilled shaft.
Mike Lambert
RE: geotech help.. skin friction, shear strength, compressive strength of drilled pier
RE: geotech help.. skin friction, shear strength, compressive strength of drilled pier
Mike Lambert
RE: geotech help.. skin friction, shear strength, compressive strength of drilled pier
RE: geotech help.. skin friction, shear strength, compressive strength of drilled pier
RE: geotech help.. skin friction, shear strength, compressive strength of drilled pier
RE: geotech help.. skin friction, shear strength, compressive strength of drilled pier
qu is the unconfined compression test.
If an undrained triaxial test, UU, was performed, then the test result is Su.
But again, undrained strength is just part of the problem. You need to have someone with experience determine an appropriate allowable foundation design.
Mike Lambert
RE: geotech help.. skin friction, shear strength, compressive strength of drilled pier
can I use this formula for end bearing as the soil bearing capacity?
end bearing = 9Su/F.S. = 9*410/3 = 1230 psf
RE: geotech help.. skin friction, shear strength, compressive strength of drilled pier
The 9Su part of the equation assumes that the bottom of the bell is more than 4 diameters below the ground surface.
You also need to confirm that the Su value is appropriate for several diameters below the bottom of the bell.
Then you need to look at settlement, constructability, and many more factors.
Mike Lambert