Solar System Deep Foundation

[august2010]

I have been assigned a task to design H Pile foundation for a solar company. The Maximum size i can go with is JIS 150x100(5.85"x3.94") because of the connection problem with the solar system.

If i use 150 x100 then using LPILE the deflection i get is 3.5" app. The minimum section that satisfies deflection is H Pile 12x84.

Can you recommend me something please?

Pile is 19.5ft in length with 3Kips lateral load on Pile Head. Distance of pile head to the ground surface is 6.5ft. so embedded depth will be 13ft.

 

[BAretired]

Could you use the 12" pile up to, say 3' above grade, then the smaller size above that?

BA

 

[msquared48]

Go back to the geotech, assuming you have one, and see if he can up the allowable lateral pressure. If not, try encasing the pile in a 30" or so diameter concrete caisson, making it a pole footing.

Remember that there are two things contributing to the lateral deflection here - (1) the stiffness of the steel pile, and (2) the lateral rotation of the entire system below the ground level.

If you do not want a larger or different pile, then your only opeion is to change (2). Going deeper will lessen the deflection too as the center of rotation will be deeper.

Mike McCann
MMC Engineering
Motto: KISS
Motivation: Don't ask

 

[cvg]

how about add more piles

 

[august2010]

Thanks a lot for the advices.

@BAretired
i recommended the same thing in my office but they dont want to get into all another connection design of piles.

@msquared48
That was the first thought came to my mind, putting the pile in a caisson. But client needs results out of LPILE and I want to know if I can design HPile in Caisson using LPILE. Please let me know! I just started my career and no one has ever designed deep foundations in my office.

@cvg
I suggested this option to my boss. but the thing is that one pile is going to have only one connection at the top with the solar systems. There is no way to connect another pile between two solar systems.

One more thing. I talked to the solar company and they said that this pile section works fine for this case but they never sent me the design.

 

[a2mfk]

"I just started my career and no one has ever designed deep foundations in my office."

I'm thinking that you guys should not be doing this project then...

 

[paddingtongreen]

Where did your soil parameters come from? Are they too conservative?

Michael.
Timing has a lot to do with the outcome of a rain dance.

 

[august2010]

@a2mfk
my company has already done a similar project before but the guy who designed it before is gone.

The problem was that client didnt want to use any concrete in the foundation. the other solution was to provide large size of pile since the soil was weak and distance from ground level to the point of application of load was almost 10 ft.

I have analysed the pile for 3 cases and waiting for the client to respond back. 1) Pile with JIS 150 x 100 2) Pile with concrete caisson. 3) Pile with large size and connection with JIS on top.

 

[PSlem]

How about 150x100 pile with wings?

 

[msquared48]

Why do you have to use LPile? Why not just do it by hand?

It's just a pole footing...

Mike McCann
MMC Engineering
Motto: KISS
Motivation: Don't ask

 

[august2010]

@msquared48

thats what I did in the beginning. I used a method from my text book elastic beams on elastic soils. But the client didnt approve of it and he wanted design of pile on a commercially accepted software. I used com624,apile and lpile to satisfy him.

I went to the site and most of the stuff that the client told us was not even their like water level was 6 inches and I was told that it was 3 feet. and soil conditions etc...

I got an email from one of the engineers with the client and I was told of max allowable deflection of 0.3" and now i got to know that it is 3".

My first design job and first design project could not be better than this!

But thanks a lot for helping me out.

@Pslem
the only problem was deflection above the ground surface but now its complete. I am sending out drawings today!
But thanks a lot for the advice. ill keep that i mind for future reference.