Interaction between shotcrete and rock : experimental and numerical study

At LKAB’s underground mines in Malmberget and Kiruna in northern Sweden shotcrete and rock bolts are the main rock support elements. A safe working environment for the miners and high accessibility to the mine are important issues. To address these issues and to improve the use of the support, LKAB initiated a doctoral thesis study on the interaction between its rock support system and the rock. The objectives of this thesis were: to identify important parameters involved in the interaction between shotcrete and rock and if necessary investigate important quantities of these parameters, to improve the understanding of the interaction of shotcrete and rock. To achieve the first objective a number of laboratory and field tests were carried out. The second objective was achived by numerical analyses. The main conclusions are: The analyses showed that the rock strength and the unevenness of the surface had a large impact on the number of failures at the interface and in the lining. Furthermore, the behaviour of the lining was sensitive to small amplitudes of the surface roughness. A high bond strength was favourable according to the analyses. The results from the field tests showed the importance of the bond at the interface. If bond failure occurs the ability to distribute and control the crack width ceases. Failure mapping in the mine showed that that a thin shotcrete layer (