Screw pile foundation - minimum embedment depth requirement?

[Canada580]

Hi,

I don't think there is specific emebedment minimum depth requirement for screw pile to work other than frost depth and uplift capacity requirement. But I am not 100%.

I got a project, minimum torque specified was 80,000 ftlb and depth of installation was around 24 feet. But contractor was saying they got 100,000 ftlb and was not able to go further than 12 feet because of rock. I did not get chance to look for there reading data sheet yet. soil was mainly stiff to very stiff clay.

will the installation be fine to take design loads using torque and capacity relation? people may argue why not. Do we need to satisfy design depth and minimum torque both?

Will appreciate for your insight on this.

Thanks.

 

[hokie66]

I think the contractor is correct, and if he has hit rock, not just a perched boulder or the like, then your specification would be satisfied.

 

[dik]

Rock is good... did you have a geotech report. 12' is normally well below frost penetration for most areas of Canada.

Dik

 

[Canada580]

I was thinking this depth of 3.5 m is not too deep to consider it as deep foundation.

 

[Okiryu]

Agree with the above comments. But I think that if the rock where they found at 12' is not the bedrock of the site, you may need to try to go deeper doing some preboring. So, take a look at the boring data and make sure that actually you can expect the bedrock at shallow depths.