1. Ohayo Gozaimas Good Morning!

4. Performance and Instrumentation of Micropiles for a Paper Mill Expansion Nadir Ansari, Matthew Janes, Daniela Ramirez of Isherwood Associates Jim Bruce of Geo-Foundations Contractors

5. Micropiles were planned for the enhancement of foundation capacity as part of an expansion to the existing Bowater Pulp and Paper Mill facility in Thunder Bay Canada. Large increases, on the order of 3800 kN, in pier capacity were required. Two piles per pier were added with maximum individual micropile working loads of 1900 kN/pile

6. Micropile Geometry
Elevation showing the three major sections of the Type 1 micropile (1900 kN).
Types 2 and 3 (1400 & 1100 kN) eliminate the upper 44 mm dia bar.

7. Micropile Sections
Typical micropile sections showing the pipe, grouted section and the inner bar.
Note the intention to pressure grout to fill the outer annulus between the pipe and the soil/rock

8. Bowater Soils Strata

11. Micropile Quick Maintained Load Test

12. Creep Analysis for Compression Load Test

13. Tension Test Results

14. Contractometer Results

15. Results of Micropile Testing
Quick Maintained Load Test
-Proved more than 2x working load of test pile
Contractometer Results
-Indicates no displacement of sensor immediately above
weathered rock
Test Question – Can this be?
2900kN load on 30 metres of 200mm diameter pile
0 displacement below 30 metres
q average = 160kPa

16. Commentary on Micropile Design
FHWA Design
-FOS steel 2.0
-FOS concrete 2.5
Calculating Actual σ
Assuming Σ compatibility
at 3800kN (Ultimate load)
-Use δ=PL/AE
or δ= σ L/E

17. Commentary on Micropile Design
- σsteel = 235 MPa or 54% yield
-σconc = 50.3 MPa or 126% yield
Ratio Asteel/Aconc
actual = 2.36
required = 17.2

18. Conclusions Pressure grouting was successful for very long piles in stiff clays and rock Use of contractometer on the very long test micropile provided controversial results Design using the FHWA Implementation Manual requires careful attention to be paid to ratio of steel and grouted cross sectional areas

19. Arigato gozaimas Thank You!