graitery tunnel– use of zsoil for complex excavations · 28th august 2009 1010 zsoil-day 2009...

28th August 2009 11

Graitery Tunnel– Use of Zsoil for complex excavationsZsoil-Day 2009

Graitery Tunnel

Use of ZSoil for complex excavations

Dominique TendonAldo BisettiJacques L’Eplattenier

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A16 – Transjuranne

Graitery Tunnel Tunnel : L = 2’462 m

South portal: L = 18 m

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N

Tunnel face

Axis

N16

Cut and cover tunnel

L = 18m

South portal excavation

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South portal - initial project - Front excavation wall

Axe N16

Strand anchors

Bar anchors

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History of excavation:

Mid 2007: Beginning of the excavation of the south portal of the GraiteryTunnel

October 2007: Movements of the front excavation wallIncrease in the tensile forces of the anchors

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5th november 2007

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Novembre 2007: Reinforcement of front wall (more anchors are added) Excavation continues

The wall movements and the increase in anchor forces are nothindered

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Geodesic mesurements – Horizontal displacements

Embankment displacements Front wall displacement (top)

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Tensile forces in strand anchors

Pinitial = 500 kN

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16th november 2007

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Novembre 2007: Reinforcement of front wall (more anchors are added) Excavation continues

The wall movements and the increase in anchor forces are nothindered

Mid-novembre 2007: Partial filling of the excavation to prevent an instability

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Décember 2007

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January - April 2008: Complementary investigations (6 additional borings) More precise geological model

Important laboratory tests campagne carried out by the EPFL

Retrofit Stability analysis using ZSoil performed by GVH

Constant interaction between the geological model, the stabilityanalysis and the scope of the laboratory testing.

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Geology – Vertical section

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Retain structure front and lateral walls:

- strand anchors AVT 5T13, Pinitiale = 500 kN

- bar anchors GFK D25mm

- bar anchors GEWI D25mm

Colluvions

Fractured marnymolasse

Compact marny molasse

Limestone

Sandstone molasse

Investigation gallery

ZSoil 3D Model

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Ground water

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Level A: 1/2 AA15, AA14, AA13, AA12, AA11 et AA10

Level C:CA12, 1/2 CA11 et CA10

Level D:DA 10

Front wall Lateral wall

Level C:CA1, CA2, CA3 et CA4

Pretressed strand anchors

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Front wall

Lateral wall

Level B: 3 clousGEWI+ 3 GFK

Level C: 3.5 GFK

Level D: 4 clous GFK

Level E: 3.5 clous GFK

Level A: 2 GEWI

Bar anchors

Level B: 3 GEWI

Level D: 5GEWI

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Ancrages passifsDisplacements for C molasse marneuse = 20 kN/m2

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Ancrages passifsDisplacements for C molasse marneuse = 20 kN/m2

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Tensile forces in prestressed anchorsC molasse marneuse =20 kN/m2

Free portion

Fixed portion

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Adjustment of cohesion using mesured tensile forces in anchors

φ' = 16°

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Redesign of the south portal retaining structure

Front wall:Anchored pile wallFireglass reinforcement for piles within the tunnel build

Lateral walls:Secant anchored pile walls

Embankment above tunnel:Permanent prestressed anchors

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Models for the design of the retaining structures:

2D models for design of piles

2D model for stability of lateral walls

2.5D model for stability of front wall

3D model for acknowledgement of previous results

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ZSoil 3D Model

Colluvions

Fractured marnymolasse

Limestone

Sandstone molasse

Sheet-pile walls

Excavation for permanent anchors

Investigation gallery

Compact molasse compacte

Horizontal beam

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Retaining structuresPermanent anchors

Tunnel face supportFiberglass bolts (GFK)

Superior horizontal beam

Pile walls

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1. Initial state

Excavation fillingmodelized by triangular

shaped horizontal forces

Existing retaining structure

(constructed before filling)

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2. Construction of the pile walls

Front and lateral pile walls

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3. Permanent anchors in embankment

Excavation and anchors

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Anchors activatedstep by step

4. Step by step excavation

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6. Demolition of piles in front of the tunnel crown Construction of the umbrella vault

Umbrella vaultLongitudinal steel tubes

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8. Excavation of the tunnel upper half and activation of the initial support

Vue of the tunnel excavation

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Displacements

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Bending moments in piles and top beam

Horizontal cross section in beam

Vertical cross section in pile wall

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Tensile forces in bar anchors on the tunnel face

Tunnel face – GFK bolts

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Tunnel in marny molasse

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Tunnel cross section

14m94

R =

7m97

Arch supportSteel ribs HEB 240 and concrete filling

Umbrella vaultLongitudinal steel tubes

First drift (upper half)

Second drift (lower half)

Support of the invertSteel ribs HEB 240 and concrete filling

Support of the coreSteel ribs HEB 240 and concrete filling

Support of the coreRock bolts

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30 m

18 m MarnyMolasse

ZSoil 2D Model

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Step 1

Initial state

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Arch supportBeam modelising the steel ribs and

concrete filling

Invert supportBeam modelising the steel ribs and

concrete filling

Umbrella vaultRadial bars modelizing the flexibility of the

longitudinal steel tubes

Base of arch supportVolumetric elements

Step 2

2a Activation of umbrella vault

2b Excavation of upper half

2c Arch and invert support

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Step 3

3a Transfer of the efforts from theumbrella vault to the arch support

3b Activation of rock bolts for coresupport

Removal of radial bars modelising theumbrella vault

Rock boltsTruss elements

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Step 4

4a Removal of first invert support

4b Excavation of lower half

4c Activation of core and final invertsupport

Core and invert supportBeam modelising the steel ribs and

concrete filling

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Step 5

5a Activation of tunnel lining

5b Transfer of efforts from initial support to lining

Tunnel liningContinuum for structures

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Problems with 2D model:

Unconfinement rate of upper half: well documented -> assumptions made in 2D ok

Unconfinement rate of core : not well documented - > specific 3D model

Stability of tunnel face - > specific 3D model

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30 m

15x2 = 30 m

4 m

5x2 + 10x1 =

20 m

27 m

18 m

MarnyMolasse

Excavation of the core and invert by steps 2m long starting from the south

portal going north.

Excavation of thelower half

ZSoil 3D Model

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Support systems

Rock boltsConstructed from the first invert

Base of arch supportVolumetric elements

Core and invert supportsShell modelizing steel ribs and

concrete filling

Arch supportShell modelizing the steel ribs and

concrete filling

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1. Excavation of upper half in one step 2. Activation of rock bolts

3. Removal of first invert and excavation oflower half by 2m long steps

Excavation steps

4. Activation of core and invert support following the excavation

5. End of excavation and activation ofinner lining

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Variable

4 m – 18 m

Arch and invert supportShell modelizing steel ribs and

concrete filling

Marny Molasse

30 m

3x2+10x1+4x2 = 24 m

3 models :

27.5 m, 34.5m

et 41.5 m

Umbrella vaultROR steel tubes

Face supportRock bolts

Tunnel face stabilityZSoil 3D Model

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1. Initial state 2. Activation of the umbrella vault

3. Activation of face support 4. Step by step excavation and support of the upper half over the first 6 meters

5. Face stability (decrementation ofc molasse from Ck to Cd)

Excavation steps

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Displacements

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Tensile forces in tunnel face rock bolts

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Friction along tunnel face rock bolts

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Conclusion:

• Use of several models adapted to specific problems

• Start with basic model (elastic, no contact, single phase) then add complexity

• Start with small model, then extend to get correct boundary conditions

• Complex models can confirm results of specific models

• For retrofit analysis, complex models cannot be sparedbut when results correspond well to in-situ measurements, the reward is worth the effort

Faster model generationRefined mesh around studied areaFaster calculation allows for more case studies

graitery tunnel– use of zsoil for complex excavations · 28th august 2009 1010 zsoil-day 2009...

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