Process for excavating a cavity in a thin salt layer

Process for excavating by dissolution a cavity in ground predominantly containing salt, the process comprising the following steps:

• producing an injection duct, an extraction duct, a void for a communication space which places in communication the injection and extraction ducts, and at least one void for a blind tunnel such that:
• the blind tunnel extends between an open end and a closed end;
• and
• the blind tunnel communicates via its open end with the communication space;
• then injecting via the injection duct a salt solvent into the communication space in order to excavate the cavity by dissolution of the salt on contact with the solvent;
• then extracting via the extraction duct the brine formed by the dissolution of the salt;
• wherein, in order to excavate the cavity, the blind tunnel is likewise excavated by circulating solvent in this tunnel, by disposing the closed end of the blind tunnel at a level which is higher than or substantially the same as that of the open end, and making the solvent pass into the tunnel via its open end from the communication space and recovering the resultant brine so that it can be extracted therefrom.