1. The French National Research Project Soil Reinforcement by Micropile Systems François SCHLOSSER - Roger FRANK Ilan JURAN - Roger ESTEPHAN 1993-1999 FOREVER

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

3. SPONSORS SPONSORS French Government 1 100 000 USD (15%) French Partners5 150 000 USD (73%) F.H.W.A Contribution 850 000 USD (12%) Total Budget 7 100 000 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. 2440.566x6=36 3050.565x5=25 396.50.564x4=16 60100.563x3=9Spacing(mm)Spacing (Ø) Length(m)Ø(mm)MicropileNumber MICROPILE GROUPS AND EQUIVALENT COMPOSITE FOUNDATIONS ( CENTRIFUGE TESTS - 20G )

9. MICROPILE GROUPS AND EQUIVALENT COMPOSITE FOUNDATIONS ( MICROPILE GROUPS )

10. MICROPILE GROUPS AND EQUIVALENT COMPOSITE FOUNDATIONS ( 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 ( I ) with confining pressure  h =  v = 50, 100 or 150 kPa CENTERC e groupC e networkNetwork / Group L/DInclinations/D CERMES5015°4--1.28 (I)5015°4--0.9 3S-(98)10020°3.521.650.83 10020°72.22.050.93 3S-(99)10020°3.51.861.690.91 10020°71.61.741.09 10020°72.55> 1 LCPC1007.3° & 9°71.611.310.81 Lizzi1007.3° & 9°71.682.221.31 MICROPILE

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

19. FOREVER Some Main Conclusions (2) 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. FOREVER Some Main Conclusions (3) Some Main Conclusions (3) 3. Micropile Networks in Sand (I D  0.5) under Vertical Loading - Double A-Shaped Network : less efficient than the equivalent group - Lizzi’s Network Efficiency not found in the centrifuge (I D  0.8)

21. FOREVER Some Main Conclusions (4) 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