ABSTRACT
Design practitioners require appropriate data for their models of the dynamic performance of ground support elements for underground excavations subject to seismic events. Practitioners do not currently have all the model data they require for design models. Ground support element test data is index data rather than similitude data, and is derived solely from drop test methods which emulate only one of several dynamic loading modes. Element distortion, abstracted for modelling purposes as strain, is able when coupled with intrinsic element properties to effectively describe and quantify element behaviour. Eleven performance indicators and three classes of test waveforms are suggested as applicable to element appraisal under strainburst, ejection and shakedown failure modes. Two test classes, “dynamic strain test—loading induced” and “dynamic strain test—distortion induced,” are discussed. Time related changes are intrinsically dynamic, so terms such as strain rate and power are suggested as better element behaviour indicators than the current emphasis on energy and force. Proof test machines that investigate strain and strain rate indicators for worst case element distortion can be a cheaper, quicker and more effective way to validate element design than using complex load test devices. Industry stakeholders are urged to support the pivotal role ground support practitioners play in selecting and validating element acceptance for seismically active mines. However the process will require consensus on changes and enhancements to the types of proof test machines and testing methodologies, and will rely on in-situ verification of element fitness for purpose.
