Frost heaving pins holding geotextiles in place in a golf course sand bunker 2

[JLemons]

Hello to everyone,

Our Golf Course industry has been using geotextiles in bunkers over soil to keep sand clean for years. They are secured in place by metal staples or plastic pins. We have seen frost heaving of these pins.

Is there a way to measure upward force of an object (pin or staple in this case) from freezing?

Jlemons

 

[Ron]

The geotextile is a membrane. Its "supports" are the pins. Frost expansion of the soil is the loading. Tributary area of 1 pin x the unit load is the "pullout" or "uplift" on the pin. If the geotextile is buried below a layer of sand, don't forget to subtract the load from the sand as this is resistance to the heaving.

 

[dhengr]

To add to Ron’s comments, there is a soil action directly on the individual pins too. It’s not really a force so much as a soil action on the pin, with very little ability of the pin to resist it. The top few inches of soil freezes around the pin head and legs, engaging them through friction and adhesion; and expands during the freezing, maybe some heaving too, and this lifts the pin through the unfrozen soil below. Then the next few inches down freezes, expands and drives the pin up further, etc. etc. When the soil thaws, it contracts away from the pin, ever so slightly, and does not pull the pin down as it settles back to its normal elevation. This cycling may happen several times a winter depending upon your locale. After a few years the pin has been lifted several inches. You could find the pins in the spring with a metal locator and push them back down, in sand traps where this is a particular problem. The actual forces caused by frost heaving can be very large, moving entire structures.

 

[JLemons]

Thanks for the informative responses guys. It sounds like a pin could with a 1/4" head could almost uplift through a layer of concrete and break it. I will need to know how much weight (resistance) would hold the pin down during the heave or at least put it back down in place if it does heave.