USE OF SOLUTION-MINED CAVERNS IN SALT FOR OIL AND GAS-STORAGE AND TOXIC-WASTE DISPOSAL IN GERMANY

The need for storage caverns for oil and ps, and repositories for toxi c chemical waste is increasing world-wide. Rock salt formations are pa rticularly suitable for the construction of cavities for such purposes . Owing to its favourable geomechanical properties, rock salt remains stable over long periods of time without support, and it can be shown that the geological barrier of the host rock remains intact for a rema rkably long time. Safety analysis must be made for each proposed site based on site-specific data. The methods of doing this are well known and related technical recommendations exist in Germany. These recommen dations apply to the planning, construction, operation and post-operat ional management of salt caverns used for the underground disposal of hazardous wastes. In particular, geotechnical site-specific safety ver ification, as required by the government's technical regulations on wa stes (TA-Abfall) under the section ''Underground Disposal'', is requir ed. This safety verification must cover the entire system comprising t he waste, the cavern and the surrounding rocks. For this purpose geome chanical models have to be developed. The steps which must be taken wh en carrying out geological engineering site explorations and when dete rmining geotechnical parameters are discussed. In addition, recommenda tions are made for the design and construction of underground reposito ries. For liquid-filled caverns, long-term sealing from the biosphere is of particular interest. In this instance it must be shown that the natural increase in pressure in the closed cavity due to long-term con vergence does not exceed the fracture pressure. A special filled test (scale 1:1) has been performed to study this.