Journal of Earth Sciences and Geotechnical Engineering

Numerical Analysis of the Large-scale Dynamic Tests of Rock Support at Kiirunavaara mine

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• Abstract

   

  The numerical analysis of four dynamic large-scale field tests conducted at LKAB Kiirunavaara mine are presented in this paper. The aim was to numerically study the behavior and response of the burden and the tested walls in field Tests 1, 2, 4 and 5. For this purpose, two numerical methods were combined, i.e. the finite element code LS-DYNA and the distinct element code UDEC. The LS-DYNA was used to calculate the blast load, and the UDEC was used to propagate the calculated load in the model where the geological conditions of the test site and the installed rock support in the field tests were modelled. The model was calibrated by comparing the velocity and displacement calculated on the surface of the opening, and the zones yielded in tension were used to study the failure mechanism developed in the burden. The numerical models were able to mimic the behavior of the jointed rock mass and the rock support fairly well. It is concluded that the number of major joint sets was the main reason to the difference between the failure development in Tests 1 and 2 and Tests 4 and 5. The numerical analysis of Tests 1 and 2 confirmed that the gas pressure in the vicinity of the test wall in those tests was minimum. In Tests 4 and 5, it was observed that, the generated fractures in the burden combined with the natural joint condition of the burden, increased the possibility for blocks to rotate and move within the burden. The complete burden damage in Tests 4 and 5 was concluded to be the be due to the ejection of rock blocks in the vicinity of the test wall upon the arrival of stress wave, and ejection of the remaining portion of the rock blocks in the burden by the gas expansion.

   

  Keywords: UDEC, LS-DYNA, Numerical analysis, Large-scale tests, Rock support.