PRESSUREMETER TEST Study case: Rhone Valley – Power Plant Presentation for SBGIMR / BVGIRM CHOOSE EXPERTS, FIND P. Debauche & S. Basire PARTNERS
PRESSUREMETER TEST – STUDY CASE 2 FEBRUARY 2011 TABLE OF CONTENTS 1. Rhone Valley power plant – Situation map 2. Rhone valley geological context 3. Site geological description 4. Power plant foundation layout 5. Required soil investigation depth 6. Recommendations for the spacing and depth of investigation based on E.C. 7 7. Geotechnical soil investigation 8. Foundation design based on Pressumeter test
PRESSUREMETER TEST – STUDY CASE 3 FEBRUARY 2011 RHONE VALLEY POWER PLANT LAYOUT
PRESSUREMETER TEST – STUDY CASE 4 FEBRUARY 2011 RHONE VALLEY GEOLOGI CAL CONTEXT
WI NDTURBI NE FOUNDATI ON 21/02/2011 5 SI TE GEOLOGI CAL DESCRI PTI ON
PRESSUREMETER TEST – STUDY CASE 6 FEBRUARY 2011 POWER PLANT FOUNDATI ON LAYOUT Foundation slab height ~ 5 m Foundation slab diameter ~ 65 m 3300 m²
PRESSUREMETER TEST – STUDY CASE 7 FEBRUARY 2011 REQUI RED SOI L I NVESTI GATI ON DEPTH Superficial foundation
PRESSUREMETER TEST – STUDY CASE 8 FEBRUARY 2011 RECOMMENDATI ONS FOR THE SPACI NG AND DEPTH OF I NVESTI GATI ONS BASED ON E.C. 7 • For high-rise & industrial structures : grid pattern with points at 15 m to 40 m distance; Spacing • For special structures (e.g. machinery foundations, etc) : 2 to 6 investigation points per foundation. • For high-rise structures : investigation depth ≥ 3* bf ; Depth • For raft foundations with several foundation elements whose effects in deeper strata are superimposed on each other : investigation depth ≥ 1.5* bB.
PRESSUREMETER TEST – STUDY CASE 9 FEBRUARY 2011 GEOTECHNI CAL SOI L I NVESTI GATI ON CPT PRESSI OMETER DI LATOMETER Module de Young E (dilatomètre) Niveau Niveau NGF Niveau NGF MPa Module pressiométrique Em MPa Pression de fluage pf Pression limite Pl* MPa NGF Module de Coulomb G (dilatomètre) 0 2 4 6 8 10 12 0 200 400 600 0 200 400 600 800 1000 1200 1400 51 51 51 49 49 49 47 47 47 45 45 45 PreDrilling 43 43 43 9m 41 41 41 39 39 39 3 m 37 37 37 35 35 35 33 33 33 31 31 31 29 29 29 27 27 27 NO DATA 25 25 25 WI TH 23 23 23 21 21 21 CPT 19 19 19 17 17 17 15 15 15 13 13 13
PRESSUREMETER TEST – STUDY CASE 10 FEBRUARY 2011 FOUNDATI ON DESI GN BASED ON PRESSUREMETER TEST (1) Limit base pressure q pu I n our case study, the raft foundation is a shallow foundation: According to fascicule 62 – titre V, the limit base stress is provided = by the formula * Q k . p pu p le where k p is the bearing factor depending on soil nature (see table here below) B, L : dimension of foundation D : Depth of the foundation ( ) 1 ∫ D = D pl * z dz e p * 0 le
PRESSUREMETER TEST – STUDY CASE 11 FEBRUARY 2011 FOUNDATI ON DESI GN BASED ON PRESSUREMETER TEST (2) p* le : the soil equivalent net limit pressure under the foundation • I n the case of a shallow foundation established on homogeneous soil layers with a thickness of at least 1.5. B below the base of foundation: P* le = pl* � Net limit pressure value prevailing at a thickness of 1.5 B • I n the case of a shallow foundation on no homogeneous soil layers between depths D and D + 1.5 B :. = ⋅ ⋅ ⋅ p * p * . p * pl * n � Net limit pressure value in the layers located on D to D + 1.5 B le l 1 l 2 n
PRESSUREMETER TEST – STUDY CASE 12 FEBRUARY 2011 FOUNDATI ON DESI GN BASED ON PRESSUREMETER TEST (3) In order to calculate the bearing capacity of a shallow foundation, the limit values for the base Q pu have to be multiplied by the following reducing factors, depending on the limit state considered: Serviceability Limit State (SLS) Ultimate Limit State (ULS) Base strength Q pu 0.33 0.5
PRESSUREMETER TEST – STUDY CASE 13 FEBRUARY 2011 FOUNDATI ON DESI GN BASED ON PRESSUREMETER TEST (4) The calculation of settlement by the pressuremeter method defined in French code (Fascicule 62 Titre V or DTU 13.12) is not applicable for of large dimensions of rafts. Settlement by the pressumerter method is limited to the soles of small sizes (3m x 3m). For raft foundation, finite element model must be performed. I n finite element model, Young modulus must be determinate. I n this studies case Ey is determinated by Dilatometer test and pressiometer test with correlation.
PRESSUREMETER TEST – STUDY CASE 14 FEBRUARY 2011 FOUNDATI ON DESI GN BASED ON PRESSUREMETER TEST (5) Young modulus correlation with pressumeter test = α The relationship usually used : E E M oed M ( )( ) + ν − ν 1 ' 1 2 ' With ν ’, Poisson = E E ( ) y oed − ν 1 ' coefficient = 0.3 E = E 0 . 74 M y α M Selection of rheological coefficient of soil α M : α M Depth (m) Lithology Geotechnical behavior 14 - 20 Marls Natural Rock 1/2 20 - 40 Sandy Marls Normally consolidated Sand 1/3 40 - 80 Marls Natural Rock 1/2 80 - 100 Sandy Marls Normally consolidated Sand 1/3
PRESSUREMETER TEST – STUDY CASE 15 FEBRUARY 2011 FOUNDATI ON DESI GN BASED ON PRESSUREMETER TEST (6) Young modulus correlation with pressumeter test Young Modulus Module de Young Ey (dilatomètre) Module de Young Ey modélisé selon la formule : Ey=0.74EM/a Significant difference between Young's modulus measured Module pressiométrique by the dilatometer tests and Young's modulus deducted by Niveau 0 200 400 600 800 1000 1200 1400 MPa the pressuremeter tests : 0 5 - Limits of correlations ? 10 15 See article O. Combarieux in “Revue française de la 20 géotechnique N ° 114”: 25 30 « L’usage des modules de déformation en géotechnique » 35 40 45 He defied for circular slab the following relationship 50 55 60 65 70 75 Where : 80 R is the radius of the foundation = 32.5 m 85 R 0 = 0.3 90 95 100
PRESSUREMETER TEST – STUDY CASE 16 FEBRUARY 2011 FOUNDATI ON DESI GN BASED ON PRESSUREMETER TEST (7) Young modulus correlation with pressumeter test Young Modulus O.COMBARIEUX Method Young Modulus Module de Young Ey (dilatomètre) Module de Young Ey (dilatomètre) Module de Young Ey modélisé selon la formule : Ey=0.32((R/R0)^(1-a)+a/2) où a=1 et 2/3 Module de Young Ey modélisé selon la formule : Ey=0.74EM/a Module pressiométrique Module de Young Ey modélisé selon la formule : Ey=0.32((R/R0)^(1-a)+a/2) où a=1/2 et 1/3 Niveau 0 200 400 600 800 1000 1200 1400 MPa Niveau 0 200 400 600 800 1000 1200 1400 MPa 0 0 - Problematic of choice of 5 5 rheological soil parameters α 10 10 15 15 With the “O. Combarieux method” 20 20 for the correlation the coefficient 25 25 α = 1 (behaviour of an over 30 30 consolidated clay) 35 35 α = 2/ 3 (behaviour of a 40 40 consolidated clay) 45 45 50 50 55 55 Same differences at great 60 60 deep with this 2 method of 65 65 correlation : 70 70 75 75 Limit of validity of the 80 80 results of pressuremeter 85 85 tests at great depth? 90 90 95 95 100 100
PRESSUREMETER TEST – STUDY CASE 17 FEBRUARY 2011 FOUNDATI ON DESI GN BASED ON PRESSUREMETER TEST (7) Calculation of settlement with finite element model (SAP) Flexible Model Estimation of settlement with load uniformly distributed over the raft of 6.3 Bar, is equal to 7.8 cm at the center of the raft
PRESSUREMETER TEST – STUDY CASE 18 FEBRUARY 2011 THANKS FOR YOUR ATTENTION.
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