Protecting Sensitive Structures from Tunnelling in Urban Environments

Transcription

1 Purdue Geotechnical Society 16 th G.A. Leonards Lecture Protecting Sensitive Structures from Tunnelling in Urban Environments Eduardo E. Alonso School of Civil Engineering Universitat Politècnica de Catalunya, Barcelona, Spain West Lafayette, April 27 th,

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3 Barcelona high speed railway crossing

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5 Terminal 2. Barcelona Airport Railway Tunnel Crossing

6 Railway tunnel under Terminal 2. Barcelona airport

7 SPT, small strain stiffness and undrained strength. Barcelona airport

8 Earth Pressure Balance Shield (EPBS) 1. Excavation wheel 2. Pressure chamber (Front support) 3. Water tight bulkhead 4. Jacks (shield forward motion) 5. Screw conveyor (Debris removal and pressure chamber control) 6. Dowel erector 7. Tunnel liner

9 Building the tunnel under Terminal 2. Barcelona airport

10 Pressures against soil at excavation boundaries

11 Basics of soil deformation around tunnels ( x) e v max x 2 2i 2 Vs 2 i max V * s Vs R 2 i 2 H 2 x * R 2i s v( x) V 2 e H 0.1%; 0.5%; 1% x ( x)? : Displacement vector goes through tunnel center

12 Damage induced by tunnelling Deflection ratio v x Damage f, l l Horizontal strain (Deflection ratio) (Simplified from Boscardin & Cording, 1989)

13 Tunnel-building interaction The building as an elastic beam

14 Modification Factors for Deflection Ratios (DR) M DR ( DR) ( DR) tunnel building greenfield * E ( EI ) 4 Soil( 10 ) Building ( B/ 2) 4 Potts & Addenbrooke, 1996

15 Effect of building flexural and horizontal stiffness (Damage category by Burland, 1995) Additional contribution by Franzius et al (2005): 3D parametric study + building weight

16 Structural model of Sagrada Familia modernist Basilica Structural model by INTEMAC, 2005

17 Model for the crossing of Terminal 2, Barcelona airport m

18 Simulation of Terminal 2 crossing. 3D Soil + Tunnel + Structure model Settlement (m) Surface settlements (m) Tunnel (Geoconsult, 2017)

19 Simulation of Terminal crossing. 3D Soil + Tunnel + Structure model

20 Contents 1. Compensation grouting Semi-analytical solution 2. Protection walls Semi-analytical solution 3. Other mitigation techniques

21 1. Compensation grouting Alcalá gate, Madrid

22 Compensation Grouting

23 TAM Tubes à Manchettes Rubber sleeves

24 TAM + Double Packer injection technique

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26 Bilbao metro Slender building Leah Manning building Complex geology Tunnel parallel and close to building Small cover to diameter ratio Isolated footings Footings on rock at one end

27 Bilbao metro Marls and Limestone

28 Bilbao metro Ground water lowering induced by tunnel construction and building settlement

29 Bilbao metro Plan view of compensation grouting boreholes

30 Bilbao metro Three levels of compensation grouting boreholes (m)

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32 Bilbao metro Monitoring

33 Bilbao metro Drilling starts Leak in tunnel face Compensation grouting starts Settlements measured in points fixed to building

34 TAM. Pressures and volumes injected Total injected volume of cement grout: 97 m 3

35 London

36 Tilt of Big Ben Tower (Simplified from Mair & Harris, 2001)

37 Tilt of Big Ben Tower (mm/55m) Tilt of Big Ben Tower, London (Simplified from Mair & Harris, 2001)

38 Amsterdam (Bezuijen & Bosch, 2010) TAM s

39 Fracture grouting (clays) Deformation mechanisms Compaction grouting (sands) For calculation purposes: A volume increase

40 A semi-analytical solution for pile foundations subjected to soil volume change Pont de Candí, Tarragona, Spain (Alonso, Sauter & Ramon, 2015)

41 Pile foundations subjected to soil volume increase at depth

42 Initial reading: September 2002 Heave profiles

43 Green Field surface heave Used for model validation

44 The problem

45 The problem

46 Solution scheme for horizontal displacements Pile group structure Soil Formulate compatibility of displacements + Equilibrium

47 Model hypothesis Homogeneous and isotropic soil Linear elastic response of all materials involved Incompressible soil (kinematic conditions dominate) Fundamental solutions Boussinesq, 1885 Mindlin, 1936 Sagaseta, 1987

48 Model validation against surface heave mm

49 Calculated vertical displacements of pile heads Vertical displacement (m) Pile number

50 Calculated and measured inclination angles ( ) of rigid pile group cap (3 x 3 piles) of Pillar 5 in five months Direction of inclination Calculated Measured (21/Nov/07-25/Apr/08) x 0,0155 0,0176 y 0,0119 0,0191

51 2. Protection walls

52 Lithological profile

53 Adopted solution Pile wall: 1.5 m diameter piles every 2 m, 41 m long Reaction beam, 3x3 m cross section connected to pile wall capping beam Vertical gap between piles to avoid groundwater barrier effect

54 (Herrenknecht EPBS) The technical challenge

55 EPBS control

56 A simplified calculation procedure for wall-tunnel interaction Hypothesis 2D Plane strain Soil: Linear elastic, Isotropic Undrained conditions (n = 0.5) Fundamental solutions Melan (1932) for concentrated line load in half-space Longanathan and Poulos (1998) for soil deformations around tunnels (Ledesma & Alonso, 2017)

57 A simplified calculation procedure for wall-tunnel interaction

58 Melan s problem Compatibility of vertical displacements + Equilibrium Vertical displacements at wall axis (x M = 0): u z = 3F 2πE s ln c2 +w 2 c+z M 1 2 ln z M c z M +c + 1 c2 c 2 +w 2 + cz M 1 (c+z M ) 2 (Melan, 1932) L & P geometry u z = R 2 Vertical displacements in half space: z H x 2 + z H 2 + z + H x 2 + z + H 2 2z x2 (z + H) 2 x 2 + (z + H) 2 2 ε ε = ε 0 exp 1.38x2 H + R z2 H 2 Ground loss * ( V s ) (Longanathan & Poulos, 1998)

59 Compatibility of vertical displacements + Equilibrium Soil displacements Wall (elastic column) Induced by tunnel excavation (L & P) Wall-soil interface forces (Melan) ( u ) N L j n j z i un j i 1 EwAw n Equilibrium Ptip Pj

60 Dimensionless coefficients controlling the solution H 1 Tunnel cover ratio (2 to 5) R 2 d R Wall distance to tunnel (1 to 3) 3 L R Wall length (1 to 10) 4 ER s E A w w Stiffness ratio (2.5 E-5 to 2.5 E-1 )

61 Effect of wall length A base case s greenfield s Efficiency s greenfield behind wall 0: no effect 1: full effect 3; 2; ; 1% Pile tip at level of invert

62 A base case Effect of wall stiffness Efficiency 3; 2; 4; 1%

63 A base case Effect of distance of pile wall to tunnel (d/r) 3; variable; 4; ; 1%

64 An elastic FE analysis reproducing the base case Discretization boundaries: Rectangle 160 m wide x 100 m deep Volume loss: Adjusted to reproduce same maximum settlement of the base case, simplified procedure Effect of pile length Effect of wall length (L/R: 2 to 8) 1 3; 2 2; 3 variable;

65 Efficiency: Simplified analytic vs FE analysis

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67 Adopted solution Pile wall: 1.5 diameter piles every 2 m, 41 m long Dimensionless coefficients: H R d R = L 8 3 R 4 = E E s w 30MPa 30000MPa 2 Aw 1 m / m

68 Effect of soil/wall stiffness on efficiency

69 Effect of pile wall length on efficiency. Sagrada Familia (L/R = 8)

70 Plan view of monitoring devices IE IE

71 Automatic surveying

72 Small strain analysis. Volume loss in computations: 0.5% V s = 0.04% Predicted (a): No loads from monument and buildings. (b): Loads applied

73 Measured vertical displacements. Mallorca street

74 Vertical shafts for TBM inspection at atmospheric conditions Padilla shaft

75 Hydromills Vertical TBM

76 Pile excavation

77 3. Other mitigation techniques Convento do Carmo after 1755 Lisbon earthquake

78 Soil improvement. Jet grouting enclosures Lisboa underground. Sodré Station

79 Soil improvement Jet grouting slabs

80 Micropile inverted tent

81 Underpinning Lisboa underground Metropole Hotel

82 Structural reinforcement

83 Controlling Volume Loss Effect of EPBS pressures on Volume loss Field data from Line 9 Barcelona underground DiMariano et al, (2016)

84 Pressures for the Crossing of Barcelona Airport Terminal 2 P1 = 2,4 bars = 1,15 x Total horizontal stress. (Greenfield validation) P2 = 0 (Shield design does not allow it) P3 = P3 (Greenfield) + 0,8 bar

85 Settlement troughs. Barcelona Airport Terminal 2

86 Settlement troughs. Barcelona Airport Terminal 2

87 Protecting Sensitive Structures from Tunnelling in Urban Environments Simplified procedures (building interpreted as a thick beam + critical tensile strains) are of limited application in singular buildings Compensation grouting Success is not always guaranteed Better results in clayey soils Protection walls A reliable procedure

88 Protecting Sensitive Structures from Tunnelling in Urban Environments Semi-analytical procedures: Good insight into the mechanics of the problem Help designing engineering solutions at a reduced effort High efficiency of modern EPBS machines Strict control of machine operations Feedback from monitoring in real time The best protection!

89 Acknowledgements o Dr. D. Simic, Ferrovial o Eng. S. Sánchez, Geoconsult o Eng. L. Prieto, Rodio Kronsa o Eng. E.V.S. Espiña, Geoconsult o Prof. A. Ledesma, UPC o Dr. A. di Mariano, UPC o Prof. P. Roca, UPC o Prof. A. Gens, UPC o Eng. M. Sondon, UPC o ADIF: Spanish Railway Administration

90 Thank you very much!