Screw-Piles, Helical Anchors and Soil Mechanics

61 Pages·2014·4.84 MB·English

Screw-Piles, Helical Anchors and Soil
Mechanics – Where are We?
Kansas City ASCE Geotechnical Seminar
January 10, 2014
Presented by

Dr. Alan J. Lutenegger, P.E.
Professor of Civil Engineering
University of Massachusetts
and
Executive Director
International Society for Helical Foundations (ISHF)
www.helicalfoundations.org
The Complexity of Design
Single-Helix or Multi-Helix?
“Tapered” or Uniform Helices?
Close or Large Helix Spacing?
Square-Shaft or Round-Shaft?
Compression or Tension?
Sand or Clay?
Plain Shaft or Grouted Shaft?
Embedment Length?
Etc.

Topics
1. Uplift of Shallow Single-Helix Screw-Piles
2. Grouted Shaft Helical Piles
3. Efficiency of Multi-Helix Anchors
4. Installation Disturbance
1. Uplift Behavior of Shallow
Single-Helix Screw-Piles

Uplift of Single-Helix Screw-Pile vs. Drilled Shaft
Uplift Load (lbs.)
0 2000 4000 6000 8000 10000 12000
0.0
0.5
)
.
n
i 1.0
(

t
n
e
m
1.5
e
c
a
l
p
2.0
s
i
D
12 in. Dia. x 10 ft. Concrete Pier
2.5
6 5/8 in. Screw-Pile with 12 in. Helix @ 4 ft.
3.0
Round-Shaft Screw-
Piles

1.Pipe Pile Installed by
Rotation Rather than Driving

2.Both Shaft and Helix are
Engaged During Installation
and Loading
Traditional Failure Mechanism of Uplift
of Shallow Plate “Anchors”
Uplift Factors for Plate Anchors in Sand