The responses of rocks to dynamic loading under multiaxial in-situ stress state are of vital significance to many engineering applications such as rock drilling and blasting. In this study, a full-scale three-dimensional (3D) numerical testing system of the triaxial Hopkinson bar is established based on com-bined finite-discrete element method (FDEM) to investigate the dynamic responses of rocks under combined multiaxial static and dynamic loading conditions.

Many of the Earth’s most fascinating natural processes are related to rock fractures.Volcanic eruptions, tectonic earthquakes, geysers, large landslides and the formation and development of mid-ocean ridges all depend on fracture formation and propagation. Rock fractures

are also of fundamental importance in more applied fields such as those related to fluidfilled reservoirs, deep crustal drilling, tunnelling, road construction, dams, geological and geophysical mapping and field geology and geophysics.

There has been great progress in understanding fracture initiation and propagation over the past decades. The results of this progress are summarised in many papers, textbooks and monographs within the fields of fracture mechanics and materials science. Much of this improved knowledge of fracture development is of great relevance for understanding and modelling geological processes that relate to rock fractures. <...>

The science of rock mechanics was developed as a result of the activities of rock engineering, basically derived from tunnels, slopes, dam foundations, and mining workings in hard rock containing discontinuities. It developed specific theories and methods to include such features, being known as a science for “discontinuous” media, while soil mechanics, the parent science, basically considers “continuum” mechanics. For the study of rock mechanics, specific equipment and apparatus were developed for laboratory and in situ investigation, requiring means to cut, perforate, sample, and test hard materials, to determine shear strength, deformability, physical properties, in situ stresses, and so on.

However, in many occasions, geotechnical and rock engineers have to deal with working sites dominated by rocks with impaired properties, such as rocks of low strength or weathered materials or rock masses with weakening aspects, as for instance, excessive jointing, faulting, solution cavities, weak inclusions, and other features which can be classified as soft rocks or weak rock masses. Its geotechnical behavior is typical of a material situated between a soil and a rock. Such materials only a few decades ago started to be investigated and characterized more appropriately and deserve a special attention, since their properties are not well-known yet, leading to uncertainties in the design and construction of engineering workings dominated by these materials <...>

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