General presentation of EUROCODE 7 Geotechnical design

Transcription

1 Brussels, February 2008 Dissemination of information workshop 1 Workshop Eurocodes: background and applications Brussels, February 2008 General presentation of EUROCODE 7 Geotechnical design Roger FRANK, Professor Ecole nationale des ponts et chaussées, Paris

2 Brussels, February 2008 Dissemination of information workshop 2 1. Introduction 2. Contents of Eurocode 7 - Parts 1 & 2 3. Some aspects of Eurocode 7-1 Characteristic values ULS Design Approaches SLS Serviceability limit states

3 STRUCTURAL EUROCODES Brussels, February 2008 Dissemination of information workshop 3 EN 1990 EN 1991 Basis of Structural design Actions on structures EN 1992 EN 1993 EN 1994 EN 1995 EN 1996 EN 1999 «Material» resistance EN 1997 EN 1998 Geotechnical and seismic design

4 Brussels, February 2008 Dissemination of information workshop 4 Eurocode 7 Geotechnical design EN (2004) : Part 1 - General rules EN (2007) : Part 2 - Ground investigation and testing

5 Brussels, February 2008 Dissemination of information workshop 5 2. Contents of Eurocode 7 Parts 1 & 2

6 Contents of Part 1 (EN ) Brussels, February 2008 Dissemination of information workshop 6 Section 1 General Section 2 Basis of geotechnical design Section 3 Geotechnical data Section 4 Supervision of construction, monitoring and maintenance Section 5 Fill, dewatering, ground improvement and reinforcement

7 Contents of Part 1 (cntd) Brussels, February 2008 Dissemination of information workshop 7 Section 6 Spread foundations Section 7 Pile foundations Section 8 Anchorages Section 9 Retaining structures Section 10 Hydraulic failure Section 11 Site stability Section 12 Embankments

8 Informative annexes Brussels, February 2008 Dissemination of information workshop 8 Annex C Passive earth pressure Annex C Active earth pressure Annexes D & E : Bearing capacity of foundations R/A' = c' N c b c s c i c + q' N q b q s q i q + R /A' = σ v0 + k p* le 0,5 γ' B ' N γ b γ s γ i γ Annex F : Settlement of foundations s = p b f / E m

9 Brussels, February 2008 Dissemination of information workshop 9 Part 2 (EN ): Geotechnical design - Ground investigation and testing Laboratory and field tests : * essential requirements for the equipment and tests procedures * essential requirements for the reporting and the presentation of results * interpretation of test results and derived values They are NOT test standards see TC 341

10 Contents of Part 2 (EN ) Brussels, February 2008 Dissemination of information workshop 10 Section 1 General Section 2 Planning and reporting of ground investigations Section 3 Drilling, sampling and gw measurements Section 4 Field tests in soils and rocks Section 5 Laboratory tests on soils and rocks Section 6 Ground investigation report > Also a number of Informative annexes

11 Brussels, February 2008 Dissemination of information workshop Some aspects of Eurocode 7-1 Characteristic values and design values ULS Design Approaches SLS and deformations of structures

12 Geotechnical properties Brussels, February 2008 Dissemination of information workshop 12 Type of test F= field L= laboratory F 1 F 2 L 1 L 2 Correlations Test results and derived values EN EN C1 C Cautious selection Information from other sources on the site, the soils and rocks and the project Geotechnical model and characteristic value of geotechnical properties Application of partial factors Design values of geotechnical properties

13 Brussels, February 2008 Dissemination of information workshop 13 Characteristic value of geotechnical parameters P The characteristic value of a geotechnical parameter shall be selected as a cautious estimate of the value affecting the occurrence of the limit state. If statistical methods are used, the characteristic value should be derived such that the calculated probability of a worse value governing the occurrence of the limit state under consideration is not greater than 5%.

14 Brussels, February 2008 Dissemination of information workshop 14 Design values of geotechnical parameters Design value of a parameter : X d = X k / γ M Design values of actions and resistances fulfilling for STR/GEO ULS : E d R d E d = E {γ F.F k } and R d = R { X k / γ M } (= at the source, MFA) or E d = γ E.E { F k } and R d = R { X k } / γ R (RFA)

15 Brussels, February 2008 Dissemination of information workshop 15 Ultimate limit states Eurocode 7-17 EQU : loss of equilibrium of the structure STR : internal failure or excessive deformation of the structure or structural elements GEO : failure or excessive deformation of the ground UPL : loss of equilibrium due to uplift by water pressure (buoyancy) or other vertical actions HYD : hydraulic heave, internal erosion and piping caused by hydraulic gradients

16 Brussels, February 2008 Dissemination of information workshop 16 EN Ultimate limit states EQU and STR/GEO E d < R d J.A Calgaro

17 STR/GEO : persistent and transient situations Brussels, February 2008 Dissemination of information workshop 17 Approach 1 Combinations A1 + M1 + R1 & A2 + M2 + R1 Or A2 + M1 or M2 + R4 2 A1 + M1 + R2 A1 or A2 + M2 + R3 3 Resistance (γ R ) Symbol Set R1 Set R2 Action (γ F ) Symbol Set A1 Permanent Unfavourable Favourable Variable Unfavourable Favourable Bearing Portance γ Rv 1,00 1,4 1,00 Sliding γ Rh 1,00 1,1 1,00 γ G 1,35 γ G 1,00 γ Q γ Q 1,50 0 Soil parameter (γ M ) Symbol Set M1 Set A2 1,00 1,00 1,30 0 Angle of shearing resistance γ ϕ 1,00 1,25 Effective cohesion γ c 1,00 1,25 Undrained shear strength γ cu 1,00 1,40 Unconfined strength 1,00 1,40 γ qu Weight density 1,00 1,00 Set R3 γ γ γ R for Spread foundations Set M2

18 Brussels, February 2008 Dissemination of information workshop 18 STR/GEO : accidental situations Actions : all values of γ F (and γ M ) = 1.0 Resistances : all values of γ R (and γ M ) depend on the particular accident Seismic situations: see Eurocode 8-5

19 Ultimate limit states (UPL) Brussels, February 2008 Dissemination of information workshop 19 buried hollow structure b T Anchored structure W T Sand slab below water level Sand Sand Water tight surface T W T P Anchorage Water tight surface Injected sand u u Examples of situations where uplift might be critical G dst;d + Q dst;d G stb;d + R d Former ground surface σ v Sand b Sand Watertight surface u lightweight embankment during flood bottom Clay of an excavation Gravel W u Clay Clay Gravel

20 Ultimate limit states (HYD) Brussels, February 2008 Dissemination of information workshop 20 Heave due to seepage of water Water low permeability soil piezometric level in the permeable subsoil Permeable subsoil Piping Sand u dst;d σ stb;d Δu dst;d σ stb;d Example of situation where heave or piping might be critical

21 Verifications of ULS Brussels, February 2008 Dissemination of information workshop 21 Ultimate limit states of static equilibrium (EQU) : E d,dst E d,stb Ultimate limit states of resistance (STR/GEO) : E d R d Ultimate limit state of uplift (UPL) : G dst;d + Q dst;d G stb;d + R d Ultimate limit state of hydraulic failure (HYD) : u dst;d σstb;d or S dst;d G stb;d

22 Brussels, February 2008 Dissemination of information workshop 22 EN Serviceability limit states SLS Verifications : E d C d C d = limiting design value of the relevant serviceability criterion E d = design value of the effects of actions specified in the serviceability criterion, determined on the basis of the relevant combination all γ F and γ M = 1.0

23 Brussels, February 2008 Dissemination of information workshop 23 Movements and deformations of structures s max δ s max settlement s, differential settlement δs, rotation θ and angular strain α relative deflection Δ and deflection ratio Δ/L ω and relative rotation (angular distortion) β (after Burland and Wroth, 1975)

24 Conclusions Brussels, February 2008 Dissemination of information workshop 24 Eurocode 7 : - a tool to help European geotechnical engineers speak the same language - a necessary tool for the dialogue between geotechnical engineers and structural engineers Eurocode 7 helps promoting research - it stimulates questions on present geotechnical practice from ground investigation to design models

25 Brussels, February 2008 Dissemination of information workshop 25 and to really conclude : It should be considered that knowledge of the ground conditions depends on the extent and quality of the geotechnical investigations. Such knowledge and the control of workmanship are usually more significant to fulfilling the fundamental requirements than is precision in the calculation models and partial factors.

26 Brussels, February 2008 Dissemination of information workshop 26 Thank you for your attention!