Stability of pillars and tabular excavations under shear loading conditions

CIM Montreal 2011
Fidelis Tawiah Suorineni, Peter K. Kaiser, Joseph Juma Mgumbwa, Reginald Dhelda Mfanga,
Abstract Rockbursts are a major hazard in deep hard rock underground mining and tunneling. To date a significant number of rockbursts still defy conventional explanations.

A review of rockburst case histories in the literature has shown that pillars and tabular excavations under shear loading are prone to rockbursting in situations where they are least expected under conventional knowledge of rockburst causes. Despite the evidence of the effects of shear loading on underground infrastructure, and the frequency of their occurrence, little is known about how this loading mechanism causes such large magnitude events and extensive damage. In this paper analytical and numerical modeling approaches are used to understand the behavior of pillars and tabular excavations under shear loading. The numerical modeling results show that pillars under shear loading are less confined than their equivalents in the same geologic environments, and are therefore more brittle and weaker. For tabular excavations under shear loading, the behaviour depends on whether such excavations are continuous, co-planar or en-echelon offset with rockbridges. Analytical results based on slit theory show releasable potential energy in tabular excavations increases exponentially with excavation half-span. The study results are important for the safe and economic extraction of orebodies under shear loading.
Keywords: Tabular excavatios, Pillars, Shear loading, Rockbursts, Numerical modelling, Analytical solution
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