What is "tunnelings"

Usage examples of "tunnelings".

The visiting officers’ quarters, like most of the older part of Starbase Twelve, had been remodeled from the far more ancient tunnelings that dated back to the days when the long-vanished Karsid Empire had used this planetoid as a base.

Did his composure mask the deep gall of worm-work, neat, lethal tunnelings serving somehow as the pathways of this Spaalg's influence within him?

There were evidences of extensive tunnelings and laborings and many tracks of carts indented in the ground, as well as spillage of ore and oil.