Pull out force calcs for casing borehole
Pull out force calcs for casing borehole
(OP)
Not sure if this is right place to put this question.
I have undeground borehole with casing pipe with grout to hold it in place. I look for basic formula to see if grout is right to hold pipe in place. I did some search looks I have to calc pull out force in this case first and then calc downward force which will be weight of pipe and media inside.
If this is correct I need to know bond strength between grout and ground rock/ soil and bond strength between grout and steel pipe.
As long as following is valid It should work: weight of pipe and media < external area by length by bond strength
Need some help.
I have undeground borehole with casing pipe with grout to hold it in place. I look for basic formula to see if grout is right to hold pipe in place. I did some search looks I have to calc pull out force in this case first and then calc downward force which will be weight of pipe and media inside.
If this is correct I need to know bond strength between grout and ground rock/ soil and bond strength between grout and steel pipe.
As long as following is valid It should work: weight of pipe and media < external area by length by bond strength
Need some help.





RE: Pull out force calcs for casing borehole
Finally there may be some factor for lab shear strength tests that may have to be applied in calculating the in-place shear strengths.
RE: Pull out force calcs for casing borehole
RE: Pull out force calcs for casing borehole
RE: Pull out force calcs for casing borehole
In the absence of test data: Kraft and Lyons (1974) state that flush (i.e. no shear keys) drilled and grouted piles have been observed to have a grout-steel friction of between 20 psi and 35 psi. The lower bound value (= 138 kPa) may be an appropriate value if the other factors are fairly similar to the case studies in that reference. These recommendations are also adopted in the offshore standard API RP2A WSD (note that API RP2A LRFD uses a value of 248 kPa for flush piles).
For the grout-soil friction, you'll be able to find countless references for the appropriate α or β factors to apply for different interfaces.
However, as stated above by oldestguy, it's always preferable to have test data.
RE: Pull out force calcs for casing borehole
Thanks
RE: Pull out force calcs for casing borehole
RE: Pull out force calcs for casing borehole
Best method is to introduce grout at the bottom and push grout to the top of the hole, Any regular 3000-6000 psi will work but microfine product makes for easier grouting.
RE: Pull out force calcs for casing borehole
Check this DFHWA publications web site: https://www.fhwa.dot.gov/engineering/geotech/libra...
https://issuu.com/anchorsystemshawaii/docs/fhwa-mi...
www.PeirceEngineering.com