ABSTRACT
Groundwater inflow into tunnels below the water table is a fundamentally transient and three-dimensional problem. Most analytical solutions for flow, however, estimate steady state flow in two dimensions. While many semi-empirical or theoretical factors involved in the calculation make accurate prediction of inflow difficult, a relative relationship between 3D heading inflow and 2D steady state inflow can be understood through analysis of the results of a robust set of numerical models, in which parameters are varied to assess their impact on transient inflow. From these results, it can be seen how the magnitude and rate of change of transient inflow, as well the time required for tunnel inflow to reach a steady state, are all significantly affected by hydraulic conductivity, hydraulic head, and tunnel rate of advance.
