Unlined invert impact on the free-flow tunnels drainage capacity

摘要

The necessity to ensure the rock mass stability presupposes, during the excavation works, the walls and arch of the runnel profile to be supported or even lined. During the construction process the invert often remains unlined for a long time, which has a specific impact increasing the drainage capacity of the tunnel being constructed in a water saturated rock medium. The aim of the study, presented in this paper, is to assess the unlined invert impact of the free-flow tunnel on hydrodynamic processes in the rock mass. The study has been implemented by the finite element method. A steady-state two-dimensional seepage flow problem is solved under the validity of the Darcy's law and assumed homogeneous rock mass. The influence of the rock anisotropy, the initial groundwater level and the relative hydraulic conductivity of the tunnel lining on the change of the hydraulic head and drained water discharge is being assessed. Results are presented in a dimensionless form and show the impact of the various parameters involved at large boundaries of variation. Such like results are given in a case of fully lined tunnel for comparison as well as others obtained by analytic methods.