Micro-pile skin friction

[dbest69er]

Hi,

I'm currently doing a design of a steel stepover structure to allow access across a conveyor. The client have requested that they want to use steel stakes/piles to tie the columns directly into a cement stabilised pavement. The standard piles (or stakes rather) are 20mm diameter by 360mm long (embedded depth).

The pile will be taking, as a worst case, 6kN uplift force and approximately 3kN of horizontal force.

I am just wondering if anyone had any ideas of how I could estimate the skin friction between cement stabilised soil and the steel pile. The only information I could find is for piles in excess of 2.5m long.

Any advice would be appreciated.

Regards.

 

[hokie66]

That's not a pile, it's a stake...or a toothpick. Why not just use a concrete pad each side?

 

[dbest69er]

As mentioned, the client requested this. I would do a footing or pad if I could. The reason for this tie down system is because the structure will be sitting on an asphalt pavement. They don't want to go digging it up because they'd have to remove sections of the conveyor to do the works and it would become too difficult.

Thank you for your abundance of help though.

Regards,

D. Best.

 

[hokie66]

I can see making the stepover in one piece, then pegging it down with something like your tent pegs. How would you get 6kN uplift on something like this?

 

[dbest69er]

From the wind. I may be a tad conservative (probably closer to 4 or 5kN) but when I treat the walkway (3.2m long x 0.75m wide x 2.2m high) as a free standing roof, and using a net porosity factor based on the size of the grating, I calculate a small but not insignificant uplift wind force. I have calculated loads based on AS1170.2 (the Australian wind code).

The load combination I used to calculate the worst scenario reaction forces is 0.9*DL + 1.0 x Wind_hortizontal + 1.0 x Wind_uplift.

Regards,

D. Best

 

[emmgjld]

Are these to be pounded to depth or bored & then driven?
My inclination is to bore/core to about a meter & then install into grout or epoxy.
Design values will take a bit of conjecture, to define the cement stabilised pavement.