ABSTRACT
Deep hard rock is in the state of high in situ stresses and subjected to dynamic disturbances during excavation. Thus, the surrounding rock is subjected to coupled static and dynamic loading conditions at depth, leading to unconventional rock failure phenomena, such as rockburst, slabbing and zonal disintegration, which are frequently reported and pose great threats to deep mining. In order to study the rock characteristics under coupled static and dynamic loading, a new method for testing the rock dynamic behaviour under medium to high strain rates is introduced in this study. A new theory and testing method for deep underground rock mass under coupled static-dynamic loads are proposed. Two types of experimental apparatus for coupled static and dynamic loads are constructed, which are a modified split Hopkinson pressure bar and a tri-axial testing apparatus, respectively. A series of experiments involving static-dynamic loads were conducted based on the two experimental setups. Rockburst phenomena of hard rock under coupled static-dynamic loads were successfully generated in the laboratory. The results of the true tri-axial unloading compression tests on granite and red sandstone specimens indicate that the unloading can induce slabbing when the confining pressure exceeds a certain level and the slabbing failure strength is lower than the shear failure strength according to the conventional Mohr-Column criterion. In addition, a new idea of non-explosive continuous mining method for deep hard rock mining is briefly introduced in the paper.
