In situ stress measurements interpretations in large underground marble quarry by 3D modeling

This paper describes the studies and the in situ stress measurements carried out to support the stability analysis of underground ornamental stones quarries. In particular, this paper describes the findings, evidence and analysis carried out at the Ravaccione and Fantiscritti quarries, which are located in the Carrara basin, Italy. Themain activities carried out during the study are starting with the characterization of the rock mass which has been done through the interpretation of data obtained from in situ geostructural surveys, combining the geometrical and mechanical characteristics of the discontinuities with the mechanical features of the rock matrix in order to assess the proper rock index in accordance with the more diffused classification systems. Further consideration regarding the tectonic stress orientation are done through the observation of kinematic indicators on brittle structures-such as faults, fractures s.l. (joints s.s., and fractures with no evidence of movement) and systems of conjugated fractures, in order to evaluate the tectonic stress main orientation for the studied area. Then several in situ measurements of actual state of stress on various location inside the Ravaccione and Fantiscritti quarries where carried out using CSIRO cells. This preliminary work lead to the geometric reconstruction of the rock mass, carried out using the computer code Resoblocks. This phase allowed, once the current excavation geometry was given, to define the geometry of a discontinuous rock mass model on which, thereafter, a numerical simulations was carried out using the computer code 3DECs. At last, the comparison between the numerical model results and the in situ tests allowed the back analysis of the site and lead to a most satisfying model calibration to be used for the provisional analysis of further excavation development.