I like the augered piles. I have been using them for over 30 years. There is some good information on the DFI web site and on Berkel and Co. web site http://www.berkelandcompany.com/apg.htm
. This is an excellent video demonstrating the process. When you specify augered piles correctly, and they are installed correctly, you wind up with larger piles than specified. This is verified by computing the theoretical volume versus the volume of grout that is placed. The grout is placed under pressure and the grout it placed while there is positive rotation on the auger. As you move to the top of the pile, you will often have a bulb much larger than the main body of the pile shaft because there is less overburden to counter the pressure of the grout being pumped into the shaft.
It really is not a big deal to place the steel post with the cage. It is just tied together and dropped inot the fluid grout as a unit. The grout is very fluid and is measured in terms of flow rate. Consolidation is not a problem. It is similar to SCC in this regard.
How you design it depends on your suppositions. You could consider the grout as hard earth and not use a cage. But if you tie the post to the cage and provide a support at the top, the installation should be easy.
If you use a drilled caisson, the cage will be required to go in the shaft prior to placement of the concrete. Because there is nothing stabilizing the earth, you actually have a higher risk of having insufficient cover than the augered pile.
Cost both out. Have the augered pile as your design and allow the caisson as a contractor's option.
The trick with augered piles is a VERY tight spec. The good contractors will not have a problem. I can name names, and it depends on where the project is located. I have had bad contractors and I have had good ones. I had a contractor awarded a job in Southern California over my objections many years ago that took 6 months to be fired. A qualified contractor came in and completed the job in about 90 days. It was a half million in piles and the bids were only about $20,000 apart. The delay the first few days ate up the delta. The other caveate is the testing. There are many good inspectors that use NDT very inexpensively. Have the inspector work with the contractor. You don't need each pile inspected with NDT, but you should have a representative sample. The tester of choice is Olson Engineering out of Colorado. The pile company of choice is Berkel out of Kansas. Have them look at your spec to see if you have culled out the bad guys.
I haven't been charging my beer rate in a while. ....That will be one six pack of any good local craft beer;>)
Regards, Harold Sprague
> Date: Fri, 28 Oct 2011 09:02:59 -0400
> From: design(--nospam--at)hodgsoneng.ca
> To: seaint(--nospam--at)seaint.org
> Subject: Highway Sound Barrier Walls
> I'm currently in a debate with another engineer regarding drilled piles
> or caissons for highway sound wall posts. I want to provide steel posts
> embedded a short length into augered concrete piles with a steel rebar
> cage around the perimeter of the pile with 76mm (3") of cover. The
> other engineer maintains that a rebar cage is not necessary if the
> galvanized steel post is extended to near the bottom of the pile.
> My position is that, due to the augering of the hole and filling in with
> concrete, it is likely that dirt will fall into the concrete or that
> uneven drilling or air pockets could lead to weakening or cracking and,
> hence, loss of cover.
> I want the rebar cage since our code states that, in seismic zones,
> non-plain concrete shall not be used for structural members where
> ductility is required.
> Anybody have any thoughts or opinions on this issue?
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