Pile Springs for Micropiles

[Ratsvein]

Good Day!

I am currently designing a 3 storey building that is to be supported by micropiles. For the preliminary design of the piles, I am looking for recommendations on how to estimate equivalent vertical pile springs to model the supports. For end bearing piles, I estimate the spring using the formula for settlement of single pile from Tomlison. I am wondering if this formula is also applicable to micropiles since end bearing capacity of micropiles are ignored and resistance is derived from bond strength of the soil - grout interface while Tomlison estimates the settlement by the combined shortening of the pile and settlement at the base of the pile. Any good source to estimate the equivalent vertical spring/settlement of this soil-grout interface? Looking for your inputs thank you very much!

 

[Retrograde]

For a 3 story building I would just model it as fixed supports.

If you really need a spring stiffness, I would assume that the pile with the biggest load deflects 10mm under working load.

Also, see this:

https://www.magnumpiering.com/wp-content/uploads/2017/01/Deflection-of-Helical-Piles.pdf

 

[EireChch]

Das's S1 + S2 + S3 method is very user friendly and is reasonably accurate in my experience.