The French standard for the application of Eurocode

The French standard for the application of Eurocode 7 to deep foundations Roger Frank, Ecole des ponts Sébastien Burlon, IFSTTAR 1

Outline Introduction – Aspects of pile design following Eurocode 7 (EN 1997 -1) 1 – Table of contents of NF P 94 -262 (July 2012) 2 – Bearing capacity from CPT (assessment of ‘model factors’ g. R; d ) 3 – Displacement under axial and transverse loads (PMT "t-z" and « "p-y" methods) Conclusions/Prospective -

Bearing capacity of piles according to Eurocode 7 (compressive/tensile « resistance » ) The design shall be based on : a) on the results of static load tests b) empirical or analytical calculation methods validated by static load tests in comparable situations introduction of ‘model factor’ γRd c) results of dynamic load tests whose validity has been demonstrated by static load tests in comparable situations d) the observed performance of a comparable pile foundation (to be supported by site investigation and ground testing).

Designing pile foundations with Eurocode 7 : * importance of static pile load tests * an innovative approach to pile capacity taking account of number of load tests or number of soil profiles (through the values) * importance of assessing serviceability of structures through displacement calculation

French standard for the Application of Eurocode 7 july 2012

NF P 94 -262 : Table of contents 15 sections and 19 annexes (98 pages +108 pages) - Main sections: combinations of actions and action effects ultimate compressive resistance (bearing capacity) ultimate tensile resistance to transverse loadings structural resistance (concrete and steel properties for piles) overall stability verifications of serviceability limit states 6

2. Bearing capacity from CPT (assessment of ‘model factors’ g. R; d ) - - 7

(Bustamante et al. , IFCEE '09, 2009) 8

The database of IFSTTAR (LCPC) 9

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Piles distribution by class and soil type for CPT profiles Pile class Pile group Soil type Total Cl 1 Cl 2 Cl 3 Cl 4 Cl 5 Cl 6 Cl 7 Cl 8 G 1 G 2 Silt and clay % Ca. Co 3 < 30% 4 3 3 3 1 20 19 1 Sand gravel 0 2 3 6 0 0 0 3 14 11 3 Chalk 2 0 0 3 0 1 1 0 7 7 0 Marl and limestonemarl 1 0 0 0 0 1 1 0 Weathered rocks 0 0 0 Total 7 5 6 12 1 3 4 4 42 38 4 12

CPT rules : base resistance qp = qo + kc qce Values of kc (for De/B > 5) 13

CPT rules: shaft resistance qs =a f sol and qs ≤ qsmax 0, 2 ≤a ≤ 2, 25 and qsmax vary according to soil type and pile category 14

0, 2 ≤a ≤ 2, 2 5 v ary ac cor din g to so il ty pe a nd p ile cat ego ry 15

Abréviation N° qq 1 FS ## ssm m 2 aa xx Technique de mise en œuvre Foré simple (pieux et barrettes) Argile % Ca. CO 3 < 30% Limon Sols intermédiaires Sable Grave Craie Marne et Calcaire. Marneux Roche altérée ou fragmentée 90 90 200 170 200 90 v ava ryr i 50 aec s 90 coe rdloi n 90 ng l tao c 90 sola ils ts 130 ype 50 ed ae 130 n d s o p FB ## Foré boue (pieux et barrettes) 90 200 170 200 FTP Foré tubé (virole perdue) 50 50 90 ___ FTR Foré tubé (virole récupérée) 90 170 ___ FSR, FBR, PU ## Foré simple ou boue avec rainurage ou puits ___ ___ FTC, FTCD Foré tarière continue simple rotation ou double rotation 170 200 200 VM Vissé moulé 200 170 ___ VT Vissé tubé 90 90 90 ___ BPF**, BPR** Battu béton préfabriqué ou précontraint 130 90 90 ___ BE** Battu enrobé (béton – mortier – coulis) 170 200 ___ 11 BM** Battu moulé 90 260 200 ___ 12 BAF** Battu acier fermé 90 90 13 BAO** # Battu acier ouvert 90 50 14 HB** # H battu 90 130 HBi** H battu injecté IGU ou IRS 16 PP** # Palplanches battues 90 50 ori 90 e d 90 50 e p 320 i ___ 50 90 17 M 1 Micropieu type I ___ ___ eu 90 ___ 18 M 2 Micropieu type II ___ ___ ___ 19 PIGU, MIGU Pieu ou micropieu injecté (type III) 200 380 320 320 20 PIRS, MIRS Pieu ou micropieu injecté (type IV) 200 440 440 500 3 4 5 6 7 8 9 10 15 lil ee 260 tc ala cga 130 te o (identical to pressuremeter) 200 90 380 rtyé 50 g 50 90 90 320 16

CPT rules – 31 tests (no injected piles; no chalk) Moy : 0. 86 Mediane: 0. 80 COV: 0. 34 Quantile for 1. 18: 85 % γRd 1 = 1. 18 17

Design value of the compressive (or tensile) capacity from ground test results ‘Model pile’ procedure : Rd = Rk/g. R = Rmod/(g. R; d 1* *g. R) with a correlation factor ‘Alternative’ procedure (‘ground model’) : Rd = Rk/g. R = Rmod/(g. R; d 1*g. R; d 2*g. R) with g. R; d 2 = 1, 1 Resistance factor (Design Approach 2 - all cases, in compression) : g. R = 1, 1 18

Model coefficient g. Rd; 1 for CPT method (and g. Rd; 2 = 1, 0 or 1, 1) g. R ; d 1 Compression g. R ; d 1 Tension All piles, excepted injected piles and piles embedded in chalk 1, 18 1, 45 Piles embedded in chalk, excepted injected piles 1, 45 1, 75 Injected piles 2, 0 19

3. Displacement under axial loads (PMT "t-z" method ) t-z curves from Ménard pressuremeter modulus EM (Frank & Zhao, 1982) for fine grained soils : kt = 2. 0 EM/B and kq = 11. 0 EM/B for granular soils : kt = 0. 8 EM/B and kq = 4. 8 EM/B

1 st example : cased screw pile in Ypresian clay (Belgium) 21

Behaviour under transverse loads ("p-y"method ) Examples of "p-y" curves from PMT results Short duration Long duration with Kf = 2 ESM 18 ----------------------- or E ------------- E s. M = EM M 4(2, 65 B/Bo)a Bo/B + 3 a 4(2, 65)a + 3 a Es. M = Ménard subgrade reaction modulus

Pile of Provins (1974) (Bigot, Bourges and Frank, 1982) 23

Conclusions/Summary New PMT rules for piles have been elaborated in France (recent standard for piles, compatible with Eurocode 7, 2012). They have been fully calibrated against the databank of more than 170 full scale static load tests on instrumented piles. These full scale tests were mainly performed at the occasion of real projects/case studies. Corresponding PMT rules have also been calibrated (with more reliability!). The important role of displacements of foundations of structures is fully recognised (more than the safety with regard to soil failure ? …) 24

Thank you for your attention ! Acknowledgments: 25