Rock mass dynamic response to extraction

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Many civil and mining engineering projects require that the rock be excavated to meet underground space design requirements, or for the purpose of extracting ore material from the earth crust. Shafts, tunnels and mining stopes are only some of the numerous examples of rock excavations widely used in civil and mining engineering projects. The process of rock extraction disturbs the equilibrium of the host rock in that the in-situ rock pressure decreases at some locations and increases at others around the excavation. This may cause instability problems leading to the fall of loose rock blocks in case of low rock pressure. In the case of high post-extraction rock pressure, the excavation may collapse violently, especially when the rock is strong and brittle. This is known as rockburst or strainburst. It is invariably accompanied by the occurrence of microseismic activities in the host rock. Microseismicity occurs as the host rock is re-adjusting itself to the sudden rise in rock pressure following extraction. Such effects are known as the dynamic response of rock to extraction - the topic of this research. In an effort to avoid disasters due to violent rock failure or rockburst, networks of microseismic sensors are installed underground to monitor the response of the rock to extraction activities on a 24/7 basis. When the data is analyzed, it is possible to identify the time, intensity and location of microseismic events and estimate the speed of rock shaking, known as peak particle velocity, and the seismic energy released from the host rock as a result of an extraction process. Much research was done in the past few decades to help advance the knowledge and understanding of the rock response to extraction. It is now possible to develop sophisticated numerical models capable of simulating complex shapes of rock excavations found in geologically complex environments, as well as the in situ rock pressure, and the planned extraction sequence. However, to date, the majority of these efforts focused on simulating the extraction process in the simpler-to-model "static" conditions, i.e. a process that is not accompanied by seismic response. This deficiency is dealt with in this research as it has created a gap between the developed static models and reality, i.e. dynamic response of the rock exhibiting burst and microseismicity. The applicant has begun in recent years to address this modelling deficiency, by developing algorithms depicting the dynamic response of rock to extraction, capable of computing post-extraction pressure, peak particle velocity and seismic energy released. This research will focus on the development and verification of algorithms for the characterization of the dynamic rock response to extraction. Subsequently, it will take the developed algorithms to real-life applications for validation in Canadian mines where tremors at great depth are of much concern to the safety of the mine operators.