Side Friction Resistance of Auger Cast Piles in Bedrock 1

[chrisrosebud2001]

Does anyone have typical values that may be used. The bedrock I am dealing with is medium hard sandstone and limestone.

 

[ishvaaag]

The disrupted rock should have DCR around 10 or so, with integral parts only half foot in a column of test cylinder extracted of 5 ft. Then I would look it mainly as gross gravel of the same material.

http://www.finesoftware.eu/geotechn...te-friction-factors-for-dissimilar-materials/

Concrete in soft disgregated middle strength rock maybe 0.55 to 0.60.

 

[chrisrosebud2001]

I was actually looking more for the strength of the bond between the rock and concrete. I am assuming that the rock can resist lateral forces and that lateral pressure is not develped against the pile. Therefore, the method of using lateral pressure x tan (external frictions angle) would not be valid.

 

[ishvaaag]

Then you have two limits: the shear strength near the altered surface within the rock, and the bond strength from concrete.

Tensile strength in the rock uses to be 10 to 15% percent of compressive atrength, and shear strength is not thought to be very dissimilar. DCR=10 woulg give allowable pressure of contact of around 2 MPa, 12.5% of which is 0.25 MPa, allowable, for shear strength.

For a DCR=10 you can estimate from correlations c=0.255 MPa coexisting with an angle of inner friction of only 15 deg sexagesimal.

Bond within the concrete in uncheckable area better not to be taken over 1 MPa ultimate, 0.66 MPa allowable.