Selecting and Adjusting Burden in Surface Mining: Key Considerations and Recommendations
In 1963, Richard Ash introduced five key ratios, known as k-factors, to simplify surface blast design. Among these, the burden ratio (KB) remains a critical factor for ensuring effective fragmentation and overall blasting performance. The burden ratio is the relationship between the burden (distance from the borehole to the free face) and the diameter of the explosive (Zhang et al., 2023). Adjusting this ratio based on field conditions is essential to achieve optimal results in surface mining operations.
Understanding the Burden Ratio
The burden ratio, typically ranging from 20 to 40, directly influences both the movement of the blasted material and its fragmentation. For instance:
A burden ratio of 20 tends to produce significant throw and good fragmentation. In practice, most mines avoid blasting at the maximum burden to prevent large boulders that are difficult to dig and transport. Instead, blasters typically use a burden ratio around 30 to balance movement and breakage.
Factors Affecting Burden Selection
Several factors influence the appropriate burden ratio for a specific blast:
Rock type: Harder rock requires a lower burden ratio to ensure proper breakage, while softer rock can accommodate a higher ratio.
Explosive type: Different explosives have varying energy levels and densities. For instance, lower-density explosives like ANFO require a burden ratio of 20-25, while emulsions are typically used with ratios between 30 and 36.
Bench height and stiffness: The stiffness ratio (KH), or the ratio of bench height to burden, also plays a role in determining how the blast energy is distributed.
Making Adjustments in the Field
When selecting or adjusting the burden, blasters can start with a standard ratio based on their explosive and rock type, then make incremental changes based on blast results: If the blast results in large boulders and insufficient movement, reduce the burden ratio to increase fragmentation.
If excessive fines or excessive material throw occurs, increase the burden ratio to reduce movement and improve the uniformity of fragmentation.
By continuously monitoring blast outcomes and fine-tuning the burden ratio, mines can achieve a balance between efficient breakage and manageable rock size.
Continuous Improvement Using WipFrag
For continuous improvement, integrating tools like WipFrag image analysis software is highly recommended. WipFrag allows real-time assessment of fragmentation after each blast by analyzing particle size distribution. By comparing actual fragmentation to the expected results based on the burden ratio, blasters can: Identify discrepancies and fine-tune future blasts.
Use the software’s deep learning tools to predict how changes in burden might influence fragmentation. Ensure that the fragmentation aligns with the crusher’s requirements, minimizing downtime and optimizing overall productivity.
#blasting
In 1963, Richard Ash introduced five key ratios, known as k-factors, to simplify surface blast design. Among these, the burden ratio (KB) remains a critical factor for ensuring effective fragmentation and overall blasting performance. The burden ratio is the relationship between the burden (distance from the borehole to the free face) and the diameter of the explosive (Zhang et al., 2023). Adjusting this ratio based on field conditions is essential to achieve optimal results in surface mining operations.
Understanding the Burden Ratio
The burden ratio, typically ranging from 20 to 40, directly influences both the movement of the blasted material and its fragmentation. For instance:
A burden ratio of 20 tends to produce significant throw and good fragmentation. In practice, most mines avoid blasting at the maximum burden to prevent large boulders that are difficult to dig and transport. Instead, blasters typically use a burden ratio around 30 to balance movement and breakage.
Factors Affecting Burden Selection
Several factors influence the appropriate burden ratio for a specific blast:
Rock type: Harder rock requires a lower burden ratio to ensure proper breakage, while softer rock can accommodate a higher ratio.
Explosive type: Different explosives have varying energy levels and densities. For instance, lower-density explosives like ANFO require a burden ratio of 20-25, while emulsions are typically used with ratios between 30 and 36.
Bench height and stiffness: The stiffness ratio (KH), or the ratio of bench height to burden, also plays a role in determining how the blast energy is distributed.
Making Adjustments in the Field
When selecting or adjusting the burden, blasters can start with a standard ratio based on their explosive and rock type, then make incremental changes based on blast results: If the blast results in large boulders and insufficient movement, reduce the burden ratio to increase fragmentation.
If excessive fines or excessive material throw occurs, increase the burden ratio to reduce movement and improve the uniformity of fragmentation.
By continuously monitoring blast outcomes and fine-tuning the burden ratio, mines can achieve a balance between efficient breakage and manageable rock size.
Continuous Improvement Using WipFrag
For continuous improvement, integrating tools like WipFrag image analysis software is highly recommended. WipFrag allows real-time assessment of fragmentation after each blast by analyzing particle size distribution. By comparing actual fragmentation to the expected results based on the burden ratio, blasters can: Identify discrepancies and fine-tune future blasts.
Use the software’s deep learning tools to predict how changes in burden might influence fragmentation. Ensure that the fragmentation aligns with the crusher’s requirements, minimizing downtime and optimizing overall productivity.
#blasting
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