Reliability-based roof stability charts for cavities in heterogeneous jointed rock masses|Carte di stabilità probabilistiche di volte di cavità in rocce eterogenee e fratturate

This paper reports stability charts for the roof of anthropic cavities expressing the ratio between the minimum rock uniaxial compression strength ensuring the equilibrium and the acting vertical stress as a function of the cavity span normalized to the roof thickness. Several numerical analyses were carried out with the 2D finite difference Code FLAC, considering the uncertainties due to the spatial variability of the rock uniaxial compression strength and the presence of discontinuities. In the frame of the reliability-based assessment, curves associated with three different probabilities of failure were calculated to delimit four different stability zones. The results showed that the safety margin is slightly influenced by the variability of the rock strength, but largely worsened by the presence of joints. The charts were then applied to several cavities in Naples, whose depth and geometric features were detected during an extensive survey in 2000.