engleski

Some Experience 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. Design and construction works required complex geotechnical investigations. On the basis of the geotechnical investigation results designs of support systems of the cut in limestone rock mass were prepared. While designing the construction of the open pits all accepted features of the reinforcement rock mass behavior were used. The support systems of the cut in the rock mass were made by the reinforcements from rock bolts and multy-layered reinforced sprayed concrete (shotcrete). During the works execution, a measuring, observing and monitoring system for the support system behavior was established. The monitor-ing system included deformation measuring in horizontal deformeters and vertical inclinometers, and obser-vations of geodetic marks. This enabled to obtain the data necessary for the stress-strain back analysis of the real behavior of excavated rock mass. An active design procedure was established which made possible changes required in the rock mass reinforcement system in cuts. The back analyses results have indicated nec-essary changes the in the approach of the construction and designing of the reinforcement systems for secur-ing the slopes of the cut in the rock mass. Performed back stress-strain analysis also showed need for the addi-tional correction in the correlations between deformation characteristics of the rock mass and rock mass classification. In this paper we present some acquired experiences during open pit excavations in limestone rock mass through some constructed buildings and observed exceptions from accepted features of the rein-forcement rock mass behavior.

open pits; monitoring; limestone rock mass

nije evidentirano