Utilisation of seismic data in the assessment of displacement and energy demand imposed on ground support by strainbursts

Conventional processing of seismic monitoring data recorded in mines often adopts models and methods established in global seismology and focused mainly on tectonic earthquakes. These models and methods make it possible to evaluate geometrical and mechanical characteristics of sources (e.g. orientation and dimensions of the slip surface or shear failure zone, the direction and amount of slip or shear deformation) and the intensity of associated ground motion (typically, peak ground velocity in the vicinity of failure and at a distance from it). Forecasting of ground motion intensity for planned mining is important for the assessment of energy demand on ground support in terms of shakedown damage. Strong ground motion temporarily increases stress around tunnels and may also deepen the depth of failure, which will cause dynamic loading of ground support due to bulking (induced strainbursting damage mechanism). A new seismic source model has been suggested in recent years. It describes seismic radiation from an episode of sudden stress fracturing around a tunnel. The model makes it possible to infer the increment in the depth of failure and duration of this process from recorded seismic signals. Application of this model to relevant seismic events (those locating to tunnels with crush-type mechanisms) can be used to: (a) establish a relation between bulking duration and increment in the depth of failure (depth of strainbursting), (b) evaluate the cumulative depth of strainbursting for tunnels of the mine, (c) assess the amount and probability of strainbursting realisations. The paper discusses these applications and their utilisation for the assessment of displacement and energy demand on ground support.