Footing Anchored On Inclined Rock Surface 2

[cap4000]

I am designing a 15 foot high concrete retaining wall that is 150 feet long on a steep 15% grade. The base for the footing is very hard and smooth diabase bedrock which will need anchoring of the the footing to it. Any suggestions on the design process for the footing and the dowels into the rock for shear resistance only will be appreciated.

 

[JAE]

I would suggest chipping in either a continuous keyway or isolated keyways along the length of the wall to take all the lateral shear forces. Dowels would also be used to simply tie the two materials (concrete and stone) together, not to resist the shear.

The keys would then be analyzed as concrete shear keys.

 

[cap4000]

JAE

Thanks for the quick response. The shear key you are describing runs along the wall for 150ft. My key/dowels into the rock is actually perpendicular to the wall to resist the sliding forces from the steep 15% grade condition.

 

[tincan]

Are you meaning to construct a sheet wall (wall--no footing)that is keyed at the base and tied back at the top similar to walers in a sheet piling wall? If so design as a sheet piling wall with tie backs.

Best tincan

 

[cap4000]

tincan

No sheet piling at all. This is a convential L shape 15 foot high cantivered retaining wall with a large toe anchored with high strength Willaims Form Eng'g 75ksi grouted dowels to the inclined rock surface. The design is still at issue with the Geotech.

 

[JAE]

good point tincan - I just assumed a wall with a footing to resist the overturning.

 

[aggman]

Along with JAE's suggestion of a shear key, I have also used steel pipes bored into the rock to carry shear. Usually I use like a 3" or 3 1/2" extra strong pipe, grouted full inside, and placed in an oversized bore hole which is also filled with grout. The idea of the oversized hole is to make sure the pipe is uniformly loaded and not point loaded due to jagged edges. I look at this somewhat as an anchor bolt for blow-out, etc and I place a cap with an open center for the portion of this pipe placed in the footer. This insures a good bond...like a headed bolt.

 

[cap4000]

aggman

I like your analysis and comparison to an anchor bolt. I am wondering if there is any type of publication/research on your XS pipe anchor design concept?? Thanks.

 

[tincan]

? L-Shaped wall with footing? Are you going to construct the footing level or on the incline?
Tincan