[TowerTalk] Looking for some foundation advice

[Steve Maki]

On 05/27/20 19:34 PM, Steve Maki wrote:
> On 05/27/20 19:15 PM, Grant Saviers wrote:
> 
>> Actually it is ok to pour concrete into a wet hole if the concrete is 
>> pumped in from the bottom. The water rises right out.  Not ok to drop 
>> concrete into water.  The mix plant, pumper and driver know how to 
>> adjust the mix a bit.
> 
> Hmm - that's not my experience. When we (drillers hired by me) install 
> caissons for tall monopoles and self supporters with 30'-50' deep 
> caissons, they just dump the concrete in. They use temporary cylindrical 
> forms to prevent cave-ins, but pay little attention to the water down 
> there. These operations are always monitored by 3rd party engineering 
> firms. On the reports I usually see *freefall concrete placement*.
> 
>> Or have a PE design a different base, there are all sorts of 
>> alternatives, plates, piers, wider and shallow, etc.  As long as the 
>> base resists the overturning moment and shear. The stock foundation 
>> UST wet stamp is on the web so should be a easy and quick job for a PE 
>> (unless they want a soils test, which in theory...  but local 
>> knowledge of conditions often is acceptable).
> 
> Agreed. A suitable foundation can be designed for above ground placement 
> if you don't mind the ugliness and the concrete cost. The key is to get 
> it engineered properly.

In fact there are many 70'-100' cellular monopoles around Detroit on 
ballast mounts. Often to avoid what is beneath the surface.

-Steve K8LX