What is a Helical Pulldown Micropile?
Learn more about helical pulldown micropile foundations
It is a system for constructing a grout column around the shaft of a standard Helical Pier Foundation System pile.
Helical Pulldown Micropile Process
To begin the process, a screw anchor is placed into the soil by applying torque to the shaft. The helical shape of the bearing plates creates a tremendous pulling force that keeps the anchor advancing downward into the soil.
After the lead section with the helical plates penetrates the soil, a lead displacement plate and extension are bolted onto the shaft. Resuming torque on the assembled shaft advances the helical plates and pulls the displacement plate downward, forcing soil outward to create a cylindrical void around the shaft.
From a reservoir at the surface, a high strength flowable grout immediately fills this void, surrounding and encapsulating the shaft. Additional extensions and displacement plates are added until the helical bearing plates reach the competent load-bearing soil. This displacement pile system does not create spoils which would require removal from the site.
Benefits of Pulldown Micropile Foundations
Benefits of this system include resistance to buckling in weak surface soils, stiffer pile (deflects less at a particular load) and additional corrosion protection in aggressive soils.
The helical pulldown micropile also develops additional capacity by combining both end-bearing on the helical plates and skin friction along the rough surface of the grout column. The result is a higher capacity Pile system.