Modelling Discharge Rates and Ground Settlement Induced by Tunnel Excavation

Preisig, G.; Dematteis, A.; Torri, R.; Monin, N.; Milnes, E.; Perrochet, P.

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Modelling Discharge Rates and Ground Settlement Induced by Tunnel Excavation

Preisig, G. ; Dematteis, A. ; Torri, R. ; Monin, N. ; Milnes, E. ; Perrochet, P.

In: Rock Mechanics and Rock Engineering, 2014, vol. 47, no. 3, p. 869-884

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Title

Modelling Discharge Rates and Ground Settlement Induced by Tunnel Excavation

Author

Preisig, G.. Centre for Hydrogeology and Geothermics, University of Neuchatel, Emile-Argand 11, 2000, Neuchâtel, Switzerland
Dematteis, A.. SEA Consulting, Via Cernaia 27, 10121, Torino, Italy
Torri, R.. SEA Consulting, Via Cernaia 27, 10121, Torino, Italy
Monin, N.. Lyon Turin Ferroviaire (LTF), Avenue de la Boisse, BP 80631, 73006, Chambéry, France
Milnes, E.. Centre for Hydrogeology and Geothermics, University of Neuchatel, Emile-Argand 11, 2000, Neuchâtel, Switzerland
Perrochet, P.. Centre for Hydrogeology and Geothermics, University of Neuchatel, Emile-Argand 11, 2000, Neuchâtel, Switzerland

Document Type

Postprint

Language

English

Published in

Rock Mechanics and Rock Engineering, 2014, vol. 47, no. 3, p. 869-884. Springer Vienna

Other Version

Publisher's version : https://doi.org/10.1007/s00603-012-0357-4

Classification

Engineering

Keywords

Tunnel excavation ; Flow rate ; Ground settlement ; Effective stress ; Analytical and numerical modelling ; La Praz ; a (m) : Lateral spacing of the aquifer ; b (1/m) : Coefficient characterising the elastic resistance of fractures to compression ; C v (1/m) : Aquifer compressibility ; d (m) : Distance between the tunnel and the surface via the aquifer ; e (m) : Aquifer thickness ; E s (Pa) : Aquifer elasticity ; g (m/s2) : Gravitational acceleration ; h (m) : Pressure head ; h 0 (m) : Pressure head prior to excavation ; H (m) : Hydraulic head ; H 0 (m) : Hydraulic head prior to excavation ; K (m/s) : Hydraulic conductivity ; K 0 (m/s) : Hydraulic conductivity at no stress ; K (m/s) : Hydraulic conductivity tensor ; L (m) : Tunnel/sector length ; n (−) : Coefficient of asperities length statistical distribution ; n (−) : Unit vector normal to the fracture plane ; n x , n y , n z (−) : Components of the unit normal vector ; p (Pa) : Water pressure ; Q (m3/s) : Volumetric discharge rate ; Q 0 (m3/s) : Volumetric inflow rate without considering effective stress ; Q red (m3/s) : Volumetric inflow rate considering effective stress ; r (m) : Radial coordinate ; r 0 (m) : Tunnel radius ; s (m) : Water table drawdown ; s 0 (m) : Drawdown at the tunnel ; S s (1/m) : Specific storage coefficient ; S sm (1/m) : Rock matrix specific storage coefficient ; S sf (1/m) : Fracture specific storage coefficient ; S sf 0 (1/m) : Fracture specific storage coefficient at no stress ; t (s) : Time ; T (m2/s) : Transmissivity ; v (m/s) : Excavation speed ; x (m) : Spatial coordinate ; z (m) : Elevation head ; Z (m) : Depth ; α (−) : Reduction factor ; α B (−) : Biot-Willis coefficient ; $$\Updelta V_z$$ (m) : Ground settlement ; λ (−) : Ratio of horizontal to vertical stress ; ν (−) : Poisson's ratio ; ρ w (kg/m3) : Water density ; ρ r (kg/m3) : Rock mass density ; ϕ 0 (−) : Porosity at no stress ; σ (Pa) : Stress ; σ h (Pa) : Horizontal stress ; σ v (Pa) : Vertical stress ; σ ′ (Pa) : Effective stress ; σ 0′ (Pa) : Fracture closure effective stress

OAI-PMH Identifier

oai:doc.rero.ch:326056

Summary

Interception of aquifers by tunnel excavation results in water inflow and leads to drawdown of the water table which may induce ground settlement. In this work, analytical and numerical models are presented which specifically address these groundwater related processes in tunnel excavation. These developed models are compared and their performance as predictive tools is evaluated. Firstly, the water inflow in deep tunnels is treated. It is shown that introducing a reduction factor accounting for the effect of effective stress on hydrodynamic parameters avoids overestimation. This effect can be considered in numerical models using effective stress-dependent parameters. Then, quantification of ground settlement is addressed by a transient analytical solution. These solutions are then successfully applied to the data obtained during the excavation of the La Praz exploratory tunnel in the Western Alps (France), validating their usefulness as predictive tools.

Modelling Discharge Rates and Ground Settlement Induced by Tunnel Excavation

Preisig, G. ; Dematteis, A. ; Torri, R. ; Monin, N. ; Milnes, E. ; Perrochet, P.

In: Rock Mechanics and Rock Engineering, 2014, vol. 47, no. 3, p. 869-884

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Modelling Discharge Rates and Ground Settlement Induced by Tunnel Excavation

Preisig, G. ; Dematteis, A. ; Torri, R. ; Monin, N. ; Milnes, E. ; Perrochet, P.

In: Rock Mechanics and Rock Engineering, 2014, vol. 47, no. 3, p. 869-884

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