1. The French National Research Project
FOREVER
The French National Research Project
Soil Reinforcement by Micropile Systems
François SCHLOSSER - Roger FRANK
Ilan JURAN - Roger ESTEPHAN

2. PARTNERS DDE DE LA MANCHE FOREZIENNE SOCASO CERMES CERCSO SCETAUROUTE
MENARD
TERRE ARMEE

3. SPONSORS
French Government USD (15%)
French Partners USD (73%)
F.H.W.A Contribution USD (12%)
Total Budget USD

4. OBJECTIVES Technology & Performance Assessment
Evaluation and Development of Design Methods
Isolated, groups and networks behavior (static and seismic)
New Fields of Applications

5. FOREVER 1 - Introduction and Objectives 2 - Experimental Tools
3 - Main Experimental Results

6. FOREVER
2 - Experimental Tools

7. FOREVER
3 - Main Experimental Results

8. MICROPILE GROUPS AND EQUIVALENT COMPOSITE FOUNDATIONS
(CENTRIFUGE TESTS - 20G) 24 4
0.5 6
6x6=36 30 5
5x5=25 39
6.5
4x4=16 60 10
3x3=9
Spacing
(mm)
(Ø)
Length
(m) Ø
Micropile
Number

9. MICROPILE GROUPS AND EQUIVALENT COMPOSITE FOUNDATIONS

10. MICROPILE GROUPS AND EQUIVALENT COMPOSITE FOUNDATIONS

11. Conclusions
The creep unit load (per micropile) decreases with the spacing of micropiles within the group.
Under axial loading, the behavior of the 6 x 6 (e=4B) is close to that of the monolithic bloc.
The Bearing Capacity of the composite foundation is closely equal to that of the micropiles increased by the Bearing Capacity of the footing.

12. Double A-Shaped Micropiles Network
(FULL SCALE TESTS)

13. VERTICAL LOADING

14. LATERAL LOADING

15. LIZZI MODELS
(CENTRIFUGE TESTS)

16. LIZZI MODELS
(CENTRIFUGE TESTS)

17. EFFICIENCY OF MICROPILE GROUPS & NETWORKS
CENTER
MICROPILE
Ce group
Ce network
Network / Group
L/D
Inclination
s/D
CERMES 50
15° 4 - -
1.28
(I) 50
15° 4 - -
0.9
3S-(98)
100
20°
3.5 2
1.65
0.83
100
20° 7
2.2
2.05
0.93
3S-(99)
100
20°
3.5
1.86
1.69
0.91
100
20° 7
1.6
1.74
1.09
100
20° 7
2.55
> 1
LCPC
100
7.3° & 9° 7
1.61
1.31
0.81
Lizzi
100
7.3° & 9° 7
1.68
2.22
1.31
(I) with confining pressure h = v = 50, 100 or 150 kPa

18. FOREVER Some Main Conclusions (1) 1. Many Experimental Tools
- Experimental Site
- Full Scale Foundations
- Calibration Chambers
- Centrifuge

19. Some Main Conclusions (2)
FOREVER
Some Main Conclusions (2)
2. Micropile Groups in Sand
- Group Effect : maximum obtained when spacing equals 4 diameters (group equivalent to the block)
- Composite Foundation (micropile foundation + cap) : the bearing capacity is equal to the sum of the independent bearing capacities

20. Some Main Conclusions (3)
FOREVER
Some Main Conclusions (3)
3. Micropile Networks in Sand (ID  0.5) under Vertical Loading
- Double A-Shaped Network : less efficient than the equivalent group
- Lizzi’s Network Efficiency not found in the centrifuge (ID  0.8)

21. Some Main Conclusions (4)
FOREVER
Some Main Conclusions (4)
- Simple reticulated networks are more efficient than groups only at large displacements
- Sophisticated (more reticulated) networks seem to be more efficient than groups

22. DESIGN OF MICROPILE GROUPS & NETWORKS UNDER STATIC LOADING
1) Large influence of the installation method, difficult to assess
2) PDA tests appear to provide a reliable quality control method
3) Group effect : important parameter for both axial and lateral loadings
4) Network effect : important parameter for lateral loading, not obvious for axial loading
5) Seismic performance discussed in the next Session