Bores head back north and get lost regularly

Usage examples of tunnels.

I understand there was a survey of existing tunnels done in the 1920s for the proposed Interborough Rapid Transit system.

Water Pit: a labyrinth of shafts and tunnels that honeycombs the heart of a small island off the coast of Maine.

Unlike earlier tunnels, the Boston Shaft was not a vertical pit, but was instead cut on a slope.

By this time, the original location of the Water Pit had been lost among the countless flooded side shafts, holes, and tunnels that riddled the heart of the island.

So many tunnels were dug that a good part of the island is waterlogged and unstable.

How else could they build underwater flood tunnels without the benefit of scuba gear?

Seismographic sensors registered some small cave-ins, but they were in adjoining side tunnels and pits, not the main shaft.

I want everyone to make as many observations as possible: the condition of the cribbing, the size and number of the tunnels, anything that seems pertinent.

Glancing down, Hatch could see Neidelman playing his beam into two ragged openings on either side of the shaft, tunnels that led off into darkness.

They began to come across additional openings cut into the cribbed walls, where tunnels branched off or secondary shafts intersected the main pit.

Until now, the horizontal tunnels opening into the side of the shaft had been crude and ragged, poorly shored, some partially caved in.

There were numerous side tunnels and shafts that were still extremely dangerous, but they had been marked with yellow tape and were off limits to all but the remote mapping teams.

There were few horizontal tunnels on the island, and almost all of them were riddled with intersecting vertical shafts.

Apparently, they discovered a badly decomposed head during a search of some railroad tunnels yesterday afternoon.

On the other hand, it could have been, say, a pack of feral dogs roaming the tunnels, attacking, killing, and dismembering.