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Method and Loading Module to Mechanically Increase Pile/Drilled Shaft End Bearing Stiffness

Description:

 

Background:

Drilled shafts are deep foundation elements constructed in soil to resist compressive, uplift and lateral loads. This process involves drilling a hole to a design depth, and filling the hole with reinforcing steel and concrete. Tip resistance is not usually accounted for when estimating the overall capacity of drilled shafts and piles due to the excess deformation needed to achieve resistance. As a result, post-grouting techniques are typically implemented to improve the stiffness and load carrying capacity of the soil, but are often associated with several limitations such as lack of reliability and repeatability. Researchers at the University of Nevada, Reno have developed an improved method to increase drilled shaft/pile end-bearing resistance.

 

Description:

Our researchers have developed systems, methods, and loading modules which account for tip resistance of overall pile/drilled shaft capacity, resulting in increased stiffness of the bearing soil. This method improves upon post-grouting techniques utilizing a mechanical mechanism to preload the soil under the shaft tip, conferring the ability to account for the gained resistance at an acceptable level of movement. Each shaft/pile is preloaded during construction to verity its load carrying capability. The disclosed modules comprise varying modifications to the associated construction including positioning of anchors for a reaction frame, positioning of rod tubes, cement slurry tubes, and a loading module within the hole, where the loading module is comprised of a base plate with a lip and a seat opening for positing and securing the loading rod and reaction frame to the pile/shaft body. This module may also be coupled with a porewater pressure dissipater to dissipate water pressure generated during earthquakes.

 

Advantages:

  • This module increases the stiffness of the bearing soil
  • This module a allows designers to confidently and systematically account for the forfeited tip resistance component in the overall pile/shaft capacity
  • This module allows users will be able to reduce shaft lengths and or diameters, thus reducing the foundation cost of a project

 

Patent and Publications:

 

 

 

UNR16-007

Patent Information:
For Information, Contact:
Shannon Sheehan
Manager, Technology Commercialization
University of Nevada, Reno
ssheehan@unr.edu
Inventors:
Sherif Elfass
Gary Norris
Keywords: