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

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

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

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

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

FOREVER 2 - Experimental Tools

FOREVER 3 - Main Experimental Results

x6= x5= x4= x3=9Spacing(mm)Spacing (Ø) Length(m)Ø(mm)MicropileNumber MICROPILE GROUPS AND EQUIVALENT COMPOSITE FOUNDATIONS ( CENTRIFUGE TESTS - 20G )

MICROPILE GROUPS AND EQUIVALENT COMPOSITE FOUNDATIONS ( MICROPILE GROUPS )

MICROPILE GROUPS AND EQUIVALENT COMPOSITE FOUNDATIONS ( COMPOSITE FOUNDATIONS )

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.

Double A-Shaped Micropiles Network ( FULL SCALE TESTS )

VERTICAL LOADING

LATERAL LOADING

LIZZI MODELS ( CENTRIFUGE TESTS )

LIZZI MODELS ( CENTRIFUGE TESTS )

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° (I)5015° S-(98)10020° ° S-(99)10020° ° °72.55> 1 LCPC1007.3° & 9° Lizzi1007.3° & 9° MICROPILE

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

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

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)

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

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