ABSTRACT

To study the mechanism of crater blast formation two blast experiments were planned, one with conventional blast with stemming column and another with air decking. The simulated results were compared with the field observation. Air deck demonstrate better utilization of explosive energy into rock breakage whereas, no proper breakage was visible from conventional crater blast observations.

An explicit numerical model (1&2) of two crater blast hole demonstrated the behavior of stress wave in the air deck and full length of conventional stemming column conditions. Movement of stemming column is allowed in model 2 to see the formation pressure rings and its effect the on rock damage. Numerical results show the improvement in explosive energy utilization through pressure rings behavior in air deck, whereas, wastage of explosive energy through ejection of stemming column are found in conventional stemming model. It is clear that working time of pressure rings increase in the model 1. Stresses and pressures are measured from various monitoring points. Damage contour marked on crushed zone around the blast hole which is equal in both models and free ground surfaces in 1m interval from blast hole. A Full Damage zone was clearly found up to 4m from blast hole in model 1, whereas, less damage zone up to 2m observed in the model 2. Stemming ejection velocity is found much higher in the model 2 as compared the model 1.

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