| Comment | The subway was built using "cut and cover" method in most places, so they basically dug a trench, built a horseshoe of brick over the top and backfilled it. The groundwater leaks in all over the place. To stop it constantly dripping on the trains and track, there are sheets fixed to the internal face that let it trickle down and around to track level, where it's directed into channels and then sumps, from where it can be pumped out.
There are generally "dips" between stations (designed to aid acceleration out of and deceleration into stations) so the water will run away from the stations to a lower point and get pumped out from there. |
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