ABSTRACT
Damaged Zone (EDZ) will be generated around the openings. Furthermore, these damages will increase with time finally leading to loss of stability, progressive contour spalling or roof fall.
In salt formations the generation of the EDZ is accompanied by mechanical damage of rock fabric on a microscopic or even on a macroscopic scale, e.g. inelastic volume increase (= dilatancy) caused by opening of grain boundaries and interconnection of fissures due to deviatoric loading creating pathways for fluids. The hydromechanical behaviour of salt formations may be significantly altered in the EDZ. Exceeding of the damage/dilatancy strength may result in a significant increase of permeability by several orders of magnitude.
