Theoretical and technological approaches
Man-made Caverns for Energy, Why and How?

In construction, elements are successively added to obtain a structure that is placed on the ground (or embedded), and the main factor of equilibrium is gravity. The elements are heavy, but initially free of internal stresses (neutral state). Any defect in an element is a cause of weakness for the structure, whether original or due to excessive stress. Prestressing and post-tensioning are used to overcome these problems. Underground structures are quite different, since they...