Some experiences during open pit excavation in limestone rock mass

For the past few years in the area of the city of Rijeka, Croatia, a few open pits in limestone rock mass were excavated. On the basis of the geotechnical investigation results designs of support systems of the cut in limestone rock mass were prepared. The support systems of the cut in the rock mass were made by the reinforcements from rock bolts and multilayered reinforced sprayed concrete (shotcrete). During the works execution monitoring system for the support system behavior was established. This enabled to obtain the data necessary for the stress-strain back analysis of the real behavior of rock mass. An active design procedure was established which made possible changes required in the reinforcement system. Performed back stress-strain analysis also showed need for the additional correction in the correlations between deformation characteristics and rock mass classification.