Boring locations-Parking Stucture 1

[JoeBaseplate]

I am looking at a 186x120 5 or 6 story parking structure and the arch is asking for boring locations. I am think of at least 3 borings: close to NE corner, center, close SW corner. Is 3 borings reasonable for this footprint?

Thanks,

 

[JoeBaseplate]

@FixedEarth: I understand the 50-60' depth for a better check and also to determine seismic site class, but typically what would be your other recommended boring depths?

 

[emmgjld]

JoeBaseplate
The depth of borings is a function of the geology, the anticipated building loads and the probable foundation types. This actually is a very difficult question to answer without a good feeling for the geology. If I know very little about a site or area, I fall back to the borings are to be at least as deep as the total usable structure is high, including basements. This boring depth begins at the anticipated building base.

I remember a coal loadout silo in Western Colorado, encountered over 120' of a very rocky, wet & soft debris fan deposits. Never did find bottom. Broke the drill auger at 30' below the ground surface and excavated a 30' pit to facilitate the 'fishing'. Took a number of shelby samples in the soil & rock mess, which ended up being the best samples of the 6 day Drilling Follies. Eventually placed the silo on a structural fill and concrete matte. Performed well for 30 years, until removed after the mine was closed.

 

[FixedEarth]

JB;

Not sure if you have on grade parking outside the parking structure, but typically, we would use 2@50 ft, 3@35 ft and 1@15 ft for outside parking, if any. See attached bor. loc. map, if you have rectangular structure. We would do all the 35 ft borings first and based on the soil stratigraphy, pick the 2 deep boring locations. If you go to the City, and for some municipalities online, you can see old grading & investigation reports. Your geotechnical firm might also be able to order some aerial photos and have the engineering geologist look into existing geologic maps. There is a lot of art to this but experienced firm should be involved.

http://www.FoundEng.com

 

[BAretired]

I think it is inappropriate for the structural engineer to be determining borehole numbers, locations or depths. These should be determined by the geotechnical engineer on the basis of local knowledge and geotechnical considerations. The architect should know better than to ask that question of the structural engineer.

BA

 

[JoeBaseplate]

BA,

That is exactly the way I see it and my response has always been that "this my opinion, final locations, numbers and depths are to be determined by the soils consultant".

There are a couple of architects whom I have been working with for a while, they just like to get structural engineer's opinion.

The rest of questions above are for my knowledge since we have a Gtech expert (FixedEarth) sharing his expertise.