Analysis of In-Situ Dynamic Ground Support Test Results with Insights Revealed by Time-Dependent Terms of Power and Strain Rate

Abstract The capacity of ground support subjected to dynamic loading is commonly expressed in terms of load, displacement, and energy absorption. Most current laboratory and in-situ dynamic tests of ground reinforcement elements utilize mass drop under gravity from a certain height to generate energy and displacement in the test specimen, but neglect to consider the power and strain rate (time factor terms) in the analysis of test results. Energy and power are very closely related parameters, where power describes how fast energy leaves or comes into a system. Power is an important parameter for describing the impact supplied to a reinforcement element and the resulting reaction. The maximum power a reinforcement element can survive found to be an effective means of making comparisons between reinforcement elements. In this research three case analyses were carried out. These were previous laboratory dynamic tests conducted at the WASM testing facility, the in-situ prototype dynamic testing experiment conducted at the Mt Charlotte Mine, and in-situ dynamic testing carried out using an advanced in-situ dynamic testing rig in nine mines across Australia and Canada. The calculated energy and other parameters from in-situ dynamic tests allowed the formulation of the input power component and strain rate. Relationships were apparent between input energy, average input power, displacement, mechanism of yielding of dynamic reinforcement elements and average strain rate for the tests. The outcomes of the time factor analysis from the three cases were compared to reveal additional information.