1. Micropile Bond Strength to Concrete
Fundamental Full Scale Test Program
Preliminary Results
Allen Cadden, P.E.
Jesus Gomez, Ph.D., P.E.
Schnabel Engineering, Inc.

2. A Privately Funded Research Project – Phase 1

3. Footing Connection What do you use for the bond stress?
Can you prove it?
Are you being conservative or unconservative?

4. Test Summary Tested Steel Bar Tested Steel Casing
Tested Casing with Weld Beads
Hole Drilled with DHH
Type I grout w:c=.45±

5. Test Setup 4”

6. Block Summary
All dimensions in inches. 1 inch = 25.4 mm

7. Construction

8. Testing

9. Preliminary Results Preliminary
1 mm
1 mm
2.3 mm
3.5 mm
3.5 mm
4.8 mm
4.8 mm
(1.4 MPa)
(5.5 MPa)
(2.1 MPa)
(8.3 MPa)

10. Summary Data Preliminary

11. Conclusions and Request
Good bond can be achieved with normal grout
Use of 200 psi allowable bond value in typical situations is reasonable.
Greater stress and strain to failure was observed with deformed steel surface.
Shrinkage may be a concern with larger annulus space.
Please provide comparative data if you have any.