Finite element simulation of a tunnel excavation in an urban environment: case study of the CEVA project

Transcription

1 Finite element simulation of a tunnel excavation in an urban environment: case study of the CEVA project M. Monfared, L. Fournier Bidoz, E. Rigaud, E. Garin,T. Kazerani 1

2 Outline Introduction of CEVA/Pinchat tunnel project Geological concept and parameters determination Tunnel construction phases FE simulations Conclusions 2

3 Outline Introduction of CEVA/Pinchat tunnel project Geological concept and parameters determination Tunnel construction phases FE simulations Conclusions 3

4 CEVA Pinchat tunnel CEVA: Cornavin-Eaux-Vives-Annemasse 16 km railways in urban area between Geneva (CH) and Annemasse (FR) Key element of the Geneva- France regional transport network Creation of five new railway stations Reduction of transport time between Geneva and Annemasse to 20 min (36 min today) 4

5 CEVA Pinchat tunnel 7 sectors Sector 1 : Cornavin Saint Jean Sector 2 : Saint Jean - La Praille Sector 3 : Carouge Bachet - Pinchat Sector 4 : Val d'arve Sector 5 : Champel Sector 6 : Eaux Vives Sector 7 : Eaux Vives - frontière 5

6 CEVA Pinchat tunnel Sector 3 Underground station of Carouge Bachet 234 m Pinchat Tunnel 2024 m Cut and covered trench of Carouge 100 m 6

7 CEVA Pinchat tunnel Clients Designers of sector 3 Pilot : partners: BG Ingénieurs Conseils SA SD Ingénierie Genève SA Solfor SA à Satigny Géotechnique Appliquée Dériaz SA à Lancy 7

8 Outline Introduction of CEVA/Pinchat tunnel project Geological concept and parameters determination Tunnel construction phases FE simulations Conclusions 8

9 Geology Geological longitudinal section of the tunnel Geneva Annemasse 235 m- clay section Cover layer Clay Moraine Alluvions anciennes Simulation section 9

10 Testing and geotechnical parameters determination In situ investigations boreholes: SPT, pressuremeter Laboratory testing: classification, direct shear, oedometric and triaxial tests Elastic properties Alluvions anciennes: E= 300 MPa and ν=0.25 Cover layer: E= 30 MPa and ν=0.3 Clay: back analyzed from the laboratory triaxial tests 10

11 Triaxial tests on clayey material Sample is extracted from 9m depth 11

12 Back analyzing of the triaxial tests Single element simulation q (kpa) Experimental results - σ c =200 kpa FE simulation- σ c =200 kpa Pore pressure (kpa) Experimental results- σ c =200 kpa FE simulation- σ c =200 kpa ε axial ε axial 12

13 Back analyzing of the triaxial tests Single element simulation q (kpa) Pore pressure (kpa) Experimental results - σ c =100 kpa FE simulation- σ c =100 kpa Experimental results - σ c =300 kpa FE simulation- σ c =300 kpa Experimental results - σ c =100 kpa FE simulation- σ c =100 kpa Experimental results - σ c =300 kpa FE simulation- σ c =300 kpa ε axial ε axial E = e p' p ref Biarez and Hicher (1994 ) ref E0 165 MPa γ 0.7 =

14 Outline Introduction of CEVA/Pinchat tunnel project Geological concept and parameters determination Tunnel construction phases FE simulations Conclusions 14

15 Cross section of the tunnel in the clayey formation 15

16 Side heading galleries excavation HEB 120 each meter Distance between HEB beams: welded wire mesh covered by shotcrete Elastic shell/beam in 3D/2D models 16

17 Armed concrete mass inside side heading galleries Elastic behavior for concrete in FE models E c =20 GPa, ν=0.2 17

18 Pre-supporting system : Umbrella arch 16 m petroleum tubes, D=159 mm, t=10 mm Overlapping:4m E umbrella =? 0.5 m Weight averaging E umbrella =4.3 GPa 0.6 m 18

19 Crown excavation HEB 180 each meter Distance between HEB beams: welded wire mesh covered by shotcrete Elastic shell/beam in 3D/2D models 19

20 Bench excavation-invert construction Ongoing project Photos will come later! 20

21 Outline Introduction of CEVA/Pinchat tunnel project Geological concept and parameters determination Tunnel construction phases FE simulations Conclusions 21

22 FE simulation 3D model 2m-Cover layer 24m-Clay 24m- Alluvions anciennes 50m 51m 22

23 Tunnel face stability c' face = 40 kpa Crown excavation 23

24 Tunnel face stability Bench excavation 24

25 0.8 cm Surface settlement Heading side galleries excavation 1.0 cm 9 m 23 m 1.0 cm 28 m 25

26 2.8 cm Surface settlement Crown excavation 1.0 cm 18 m 36 m 1.0 cm 28 m 0 Construction steps Normalized settlement (%) End of side heading gallery excavation End of crown excavation

27 FE simulation 2D model Stress reduction method: λ or β parameter is estimated by fitting the surface settlement between 3D and 2D models λ=0.25 λ=0.4 27

28 Back analysis of the surface settlement Monitoring program Excavation direction 40 m 10 m MS1 MS2 28

29 In-situ surface settlement Heading side galleries excavation Distance to tunnel axis (m) Normalized settlement (%) MS1 MS2 HSS model-e 0 =165 MPa HSS model-e 0 =140 MPa HS model 29

30 In-situ surface settlement Crown excavation Distance to tunnel axis (m) Normalized settlement (%) MS1 MS2 HSS model -E umbrella arch =4.3 GPa HSS model -E umbrella arch =0.4 GPa HS model-e umbrella arch =0.4 GPa

31 Conclusions Hardening soil parameters are successfully estimated from the laboratory tests Tunnel face stability is verified by using the 3D FE model For heading side galleries the HSS model predict well the measured surface settlement however HS model predicts almost 3 times the settlement Umbrella arch Young modulus has significant effect on the predicted surface settlement The Young modulus by weight averaging predicts 50% error in settlement prediction An ten time smaller Young modulus is needed to predict correctly the in-situ settlement 31

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