Design of column footing on rock with passive rock dowel

[ssbear]

Hi there,

My current task involves a design of column footing foundation on rock. Due to large uplifting force from wind, the footing size gets quite big to achieve the stability FOS. Therefore I am wondering if it is possible to use passive rock dowel in the calculation for the uplifting force.

I am new to foundation design and I look up online but didn't find too much resources about this. Any recommendation or references that I can use would be appreciated.

Regards,

Eric

 

[emmgjld]

Yes, dowels can be used. Analise, Design & Install as Rockbolts or micropiles, if loads are high.

 

[hokie66]

You can use rock anchors. When designed for tension, I wouldn't call them "dowels", because dowels are normally for shear.

 

[cvg]

rock anchors are generally tensioned, so I would not call them passive either.

 

[hokie66]

cvg,
That is probably true for most uses of rock anchors, but when used to resist uplift due to wind, I think the most common way is just to grout them in. In competent rock, it is sometimes much more economical to drill a hole and grout in a reinforcing bar than to provide a big hunk of concrete. Depends a lot on the availability of equipment for the different methods for providing ballast against uplift.

 

[ssbear]

Thanks, emmgjld and hokie66. When comes to the calculation of bearing pressure due to the wind load(it is uplifting and overturning moment), how do I include the strength of the passive rock anchor? Is there any reference or standard that I can use?

Eric