Interpreting Geotech Report for Allpile Input - Modulus of Subgrade Reaction (kcf)

[ndalle03]

I am determining the embedment for W6x9 piles to resist lateral loads in the range of 1.25-1.5kips to support a solar structure. We typically do our own soil testing on site, however this project is unique. The geotechnical report provides a "Modulus of Subgrade Reaction (kcf)" in the range of 60-200+ in multiple borings. I am using Allpile 7 for analysis. The lateral analysis input for Allpile is "K" which is the modulus of subgrade in units of (lb/in^3) and "e50".

The input for K is in the range of 0-2000 lb/in3. If the geotech report provides "Modulus of Subgrade Reaction" of say 60kcf --> 60 x 1728 = 103680 k/in3 --> 103,680,000 lb/in3. I'm not a geotech guy, therefore this doesn't make much sense to me.

Ultimately, what shall I input into Allpile for K - modulus of subgrade (lb/in3) when given Modulus of Subgrade Reaction (kcf) from a geotech report of say 60? Thanks so much for your help!

-Nick

 

[oldestguy]

Interesting that someone can take a value for the vertical deflection of a 30" diameter plate on a roadway subgrade and apply it to the lateral resistance of a pile under lateral load. Wishful thinking.

 

[jayrod12]

isn't 60 k/ft3= 60/1728=0.0347k/in3=35lbs/in3 ?

just saying,

 

[tim1963]

How do you like using ALLPILE? It looks like it performs the same lateral analysis as LPILE but easier to use and perform a lot more. I'm also a structural engineer and I'm starting a new job with a solar company and I'm trying to determine what is the best software for pile design.

 

[GeoPaveTraffic]

Obviously missed this post originally.

Just another expample of someone using software without understanding the input values.

Garbage in = garbage out has never been truer.

Mike Lambert

 

[a2mfk]

At the risk of sounding jerky, which I do a lot anyway, instead of posting a question to a bunch of strangers on a message board (a very good message board mind you), why not just call the geotech who wrote the report and ask them for this information or a clarification? Tell them you are a structural engineer and not a geotech and they will help you. This is what a consultant team is for. In my pile experience (as a structural engineer), I gave the geotech the loads and they designed the pile capacity (of the soils).

But I do agree with the other posters, you should be careful using software to solve a problem you do not completely understand.

Also, not having designed anything like that in a while, and not knowing your soil types, 1500lb applied at the ground surface to a W6x9- I am guestimating 10ft embed? Wait- do you have uplift too?

Steel piles for a solar panel structure? It would seem like shallow auger cast concrete piles may be a better option. Maybe you are extending these up to be the columns also, which would make sense.