Dewatering, waterproofing and drainage - Tunnel Engineering: Basics and Additional Services for Design and Construction - page 187

a spring. Low-level karst holds the water percolating from the surface in an underground
basin. If a tunnel is driven through such a low-level formation, the water can pour into
the tunnel at high speed under great hydrostatic pressure and in great quantities of many
100 m 3 /min (which happened for example in the Mont d'Or Tunnel [238]). The water also
often carries suspended particles, bed load and sand.
Figure 5-1 Water
conditions in a karst rock
mass [238].
5.2.1.2 Forms of underground water
After the percolated rainwater has infiltrated through the unsaturated zones of subsoil, part
of the water flows above the groundwater table into natural discharges (interflow). The
remainder reaches the saturated zone and enters the groundwater. This process is called
percolation, the formation of new groundwater.
Water inflow. According to L. Müller [160], underground water can enter an artificial
cavity in very varied forms (Table 5-4).