Dynamic modelling of rock fracturing by destress blasting

Rockburst control measures have been in practice with continued efforts for improvements since the beginning of the 20th century. The thesis concentrates on the evaluation of destress blasting, which is an important pro-active rockburst control measure. The concept of destress blasting is based on the fracturing of highly stressed rock mass by detonating explosive charge within it. The concept has been carried out ever since the first reported use in a Canadian coal mine circa the early 1930s. Since then, many mines across the continents have applied this technique using a trial-and-error approach with mixed successes. To date, the application lacks scientific base.; The aim of this thesis is to identify the governing mechanisms associated with destress blasting applications. A holistic approach is undertaken, which involves a critical analysis of the reported field evidences, development of a numerical procedure and detailed investigations at the micro-mechanical level to investigate the fracturing of rock under confinement by different types and magnitudes of explosive energy.; A numerical procedure is developed in the thesis that carries promising potential to improve the understanding on rock fracturing by explosive energy as well as provides a platform to develop means for enhancing explosive energy utilization. The procedure is validated with reported field observations.; Analyses of destress blasting is made through dynamic modelling by simulating discrete fractures using the developed procedure. A normalized parameter ℓ ci is introduced to investigate fracturing extent after destress blasts. The investigations revealed that destress blasting produces limited fractures aligned along the principal stresses. The fracturing extent reduces with the increase in the confinement. The study indicates that the current practice of destress blasting seemingly provides more psychological benefits than factual benefits from the desired destressing.; The study also introduces a non-dimensional parameter, betaij , which characterizes destressing effects. The parameter not only adequately explains destressing phenomenon, but also offers clarifications to seemingly inexplicable reported field observations of destress blasting. Local fractures around the boreholes aligned along the principal stresses are found to be the cause of reported local stress concentration and rock stiffening post to destress blasting against the desired stress relaxation and softening.