Apparatus and methods for underground structures and construction thereof

An underground structure comprising:

• a plurality of rings creating an enclosed area defined by a first end and a second end and an internal diameter, wherein each ring includes a plurality of segments that define the internal diameter, wherein one segment of each ring is a key segment, wherein the plurality of segments includes a first segment and a second segment, wherein the key segment is between the first segment and the second segment, and wherein the key segment is configured to provide a seal between the first segment and the second segment;
• at least one post-tensioning cable configured to hold together the plurality of segments within each ring, wherein the at least one post-tensioning cable runs through a first conduit in the plurality of segments;
• and
• grout between the plurality of segments and earth surrounding the plurality of segments.