The survey of underground exploitation rooms in marble quarries: first data from the in situ monitoring.

The underground exploitation of ornamental stone, particularly when exploited with mechanized techniques (diamond wire or chain saw) creates big voids in relatively short time. This locally involves the continuous (relatively quick) intensification of the stress state of the exploited rock mass particularly near the cutted free surfaces (slopes, walls, roofs, ...). As a result the stress-strain state of the abandoned support elements of the exploited underground chamber (pillars and diaphragms) and therefore their stability conditions vary with the progress of the exploitation. This implies the need of a continuous monitoring. Besides,not less important to the stability assessment of the underground exploitation chamber it is the role of the natural discontinuities. This involves the knowledge of the attitude and of the geomechanical strength characteristics of the joints in comparison to the free surfaces of the exploitation void as well as of the support elements.