In situ stress measurement near faults and interpretation by means of discrete element modelling

The design of underground caverns of significant size and of complex geometry is often accompanied by the use of numerical models able to estimate the range of stresses and strains induced by the excavations and, consequently to evaluate the stability of the caverns. In this context, it is convenient to estimate the natural state of stress of the rock mass, the mechanical properties of the rock matrix and the discontinuities and to carry out in situ measurements to calibrate the model. In the Carrara basin (Italy) there is a huge number of underground excavations that need to be monitored and, for this purpose, a series of models and in situ measurements have been performed. This study aims to point out the difficulties involved in understanding the in-site measured stress. A series of tests were conducted in Carrara, in an underground marble quarry site, focusing to study the complex tectonic environment in the area. A series of comparisons between 3D DEM numerical models has been performed in order to understand the influence of the presence of the main faults on the in situ state of stress. Some final comments regarding the variability of stress fields in faulted rock masses are provided.