1-Initial support; 2-Impermeable layer; 3-Tunel arch (inner shell); 4-Groundwater; 5-Drainage rubble; 6-Arch drainage; 7-Base of cast-in-place concrete; 8-Groundwater collecting pipe (600mm); 9-Tunnelwater collecting pipe (250mm); 10,11-Cable collector; 12-Rails
<a href="//commons.wikimedia.org/wiki/User:W.Rebel" title="User:W.Rebel">W.Rebel</a>
CC BY 3.0
<span class="int-own-work" lang="en">Own work</span>