Abstract
Ground-water inflow created problems during the construction of the 8.8 km Kaimai Rail Tunnel. After the cement tunnel shell was completed, drains were constructed to contain the water. To assist the decision on whether to grout and where to grout, a series of flow gaugings were carried out over a six month period. Flow velocity and water temperature were measured at 100–500 metre intervals to identify the regions of inflow.
The gauging programme successfully identified two regions of ground-water inflow that would require grouting if a “dry” tunnel was desired. The western end (0–1,500 m) had a small total inflow of 55 1/s or 0.04 1/s/m. The eastern end (3,600–8,854 m) had a greater inflow, 230 1/s over a greater length of tunnel (5,254 m) (0.04 1/s/m). Between these two regions there is a net loss of 50 1/s from the tunnel. This pattern in inflow and outflow is considered to be the interception of the ground-water flow system. Water temperatures, although less definitive, show a similar pattern of inflow. The variation in water temperatures between the west (25°C) and east 30–40°C) may result from depth of flow path.
