Boring location and amount of borings
Boring location and amount of borings
(OP)
A quick question. I have a project for a foundation engineering class and must choose the location and amount of borings for a 16 story structure that measures approx. 320' in length and 160' in width. I was wondering how many borings are necessary and the general location of said borings? Should they be at the corners, along the walls, in the middle, etc?
Thanks
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RE: Boring location and amount of borings
RE: Boring location and amount of borings
RE: Boring location and amount of borings
I'd say for a 320x160 footprint, I'd go with the four corners and the center (i.e., 5 total). You could also go with six borings each along the perimeter and 160 ft apart.
Now how deep? For a 16 story building and to get to where the change in effective stress is less than 10 percent of the existing overburden pressure, you'd likely have to go pretty deep - maybe like 60 or 80 ft, unless you happen to know there is some intact granite within 30 ft or so. . .
f-d
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RE: Boring location and amount of borings
RE: Boring location and amount of borings
RE: Boring location and amount of borings
If there is no budget and if the client is a repeat client, he usually will go along with any thing you say.
Then, after reviewing the number chosen, (five seems ok), reserve the possibility to go back and do more, or to go deeper, to search out apparent variations.
As to how deep, you might use a simple rule that borings go to the depth where added stresses are below 10 percent of existing stress. This added stress includes any grade raising inside as well as outside. Neglect unloading of a basement as a starter.
RE: Boring location and amount of borings
As others have said, the question is too open ended. In the real world you would ask for some additional information.
RE: Boring location and amount of borings
I agree with grabbens approach about stimating the boring depth, the only problem is not all the time you will have a 3 ksf bearing capacity, of course, this depends on the experience of the geotech engineer in the area.
IF you have less than than 3 ksf, you might need more information.
According to what I have seen, the deepest boring is located on the elevators as the heaviest loads are located in this area. Then, you can distribute (depending on the area of the site) the rest of the borings on the columns.
These borings don;t need to have the same depth, even though the deeper the more info you have. Also remember, you might be fighting for a project, your competitors sometimes might come up with shorter borings, so sometimes conservatism doesn't help.
RE: Boring location and amount of borings
In our example, 16 story hight, we get (10 x (7)ft + 4ft = 74 ft. You would probably make this the depth of the deep borings and take several intermediate depth (30 to 40)ft borings.
As for location, I am partial to S or Z shaped layout.
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