Question:
A square pattern of blasting is shown in the figure. For the case of simultaneous blast, identify the zone of no fragmentation.
A square pattern of blasting is shown in the figure. For the case of simultaneous blast, identify the zone of no fragmentation.
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In multi-hole blasting, the center of symmetric patterns often receives balanced stress waves, creating zones of little or no fragmentation.
Updated On: Dec 17, 2025
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The Correct Option is D
Solution and Explanation
Step 1: Understand fracture zones around blast holes.
Each blast hole creates a circular fracture zone around it. When multiple holes are blasted simultaneously in a square pattern, these circular zones overlap.
Step 2: Where does fragmentation NOT occur?
Fragmentation is maximum within the fracture circle and in the regions where fracture zones overlap.
However, at the center of the square, where all four circles just touch but do not overlap significantly, the stress waves tend to cancel out.
Step 3: Identify the unfragmented zone in the figure.
In the given diagram, the purple-shaded central region represents the zone of no fragmentation, where the explosive effect does not create sufficient tensile stress to break the rock.
This region is labeled as R.
Thus, zone R is the region of no fragmentation in a simultaneous blast.
Final Answer: (C)
Each blast hole creates a circular fracture zone around it. When multiple holes are blasted simultaneously in a square pattern, these circular zones overlap.
Step 2: Where does fragmentation NOT occur?
Fragmentation is maximum within the fracture circle and in the regions where fracture zones overlap.
However, at the center of the square, where all four circles just touch but do not overlap significantly, the stress waves tend to cancel out.
Step 3: Identify the unfragmented zone in the figure.
In the given diagram, the purple-shaded central region represents the zone of no fragmentation, where the explosive effect does not create sufficient tensile stress to break the rock.
This region is labeled as R.
Thus, zone R is the region of no fragmentation in a simultaneous blast.
Final Answer: (C)
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