Progress with empirical performance charting for confident selection of ground support in seismic conditions

Abstract

The methods available for estimating dynamic-capable ground support requirements need to contend with the extreme variability of the mining environment in dynamic conditions, and uncertainties in knowledge of seismic-related data. The site geotechnical engineer, with the task of selecting a ground support scheme, is searching for a sufficient engineering result in the face of this variability and uncertainty. While knowledge has progressed rapidly in the field, it is not yet possible to have full confidence in mechanistic selection methods because they depend on various assumptions, and do not cater for variability and uncertainty in operational mining. The empirical chart approach by contrast bypasses many assumptions and accommodates the variability, so it can stand as an operational tool. The empirical approach in this paper is based on underground observations of seismic damage and the performance of ground support at three Australian mines. It defines working relationships between peak particle velocity due to seismicity, the load and energy dissipation capacities of ground support, and the damage occurring in excavations. The charts facilitate selection of the required ground support load and energy dissipation capacities for a defined dynamic environment. A key advantage of the empirical approach is that it is calibrated to the peculiarities of the specific mine site. The charts have also given insight into criteria that indicate whether a support scheme is adequately resistant against failure of weak links.