Semi-analytical solution for groundwater ingress into lined tunnel.

A semi-analytical solution for the groundwater ingress into a lined tunnel in a semi-infinite aquifer is derived based on the conformal mapping technique. The new solution considers the property of the lining, such as the permeability coefficient of the lining as well as the external and internal lining radii. A numerical model is established using the software COMSOL to verify the semi-analytical solution, and a good agreement is found. Parameters including water layer thickness, burial depth of the tunnel, permeability coefficient of the lining and the lining thickness are discussed in detail. This paper explains why the water ingress obtained from early research should be reduced by Heuer’s empirical factor 1/8. Moreover, an optimal burial depth is found when the permeability of the lining is close to the permeability of the aquifer. [ABSTRACT FROM AUTHOR]