Answer & Solution
Answer: Option A
Solution:
The correct answer is option A, Burden.
Primary blasting is a technique used in mining and construction to break rock or concrete using explosives. The degree of fragmentation refers to the size and distribution of the pieces of rock or concrete after blasting.
The burden is the distance between the explosive charge and the free face of the rock or concrete. By increasing the burden, the explosive energy is spread over a larger area, which can lead to a decrease in fragmentation. On the other hand, decreasing the burden concentrates the energy in a smaller area, resulting in increased fragmentation.
Therefore, the correct way to increase the degree of fragmentation in primary blasting is to increase the special charge (the amount of explosive per unit length of the borehole) and decrease the burden.
Option B, Spacing, refers to the distance between the boreholes and has an impact on the overall effectiveness of the blast, but not directly on the fragmentation.
Option C, Height, refers to the depth of the borehole and has a minimal impact on fragmentation.
Option D, Density, is not directly related to fragmentation, but it may affect the strength of the rock or concrete being blasted.
