In open-pit mining, the inter-ramp angle refers to the angle of the slope between two consecutive ramps or haul roads, encompassing multiple benches. The overall slope angle (OSA) is the angle measured from the toe of the pit wall to the crest of the highest point, encompassing all benches, ramps, and haul roads within the open pit mine. It’s a critical parameter in mine design, influencing both the economics and safety of the operation. Let’s explore the differences between those concepts in this article.
Interramp slope angle
- The interramp slope angle is the angle measured between the toes and crests of benches, specifically between the bottom toe of one bench and the top crest of another but excluding any haul roads or ramps that may be present within the slope.
- It represents the average angle of the pit wall over several benches, considering only the benched sections and not the flatter sections created by ramps or haul roads.
- This angle is critical for analyzing the stability of the benched portions of the slope, optimizing catch bench widths, and is often used in geotechnical and operational design to ensure safety and efficiency.
Overall slope angle
- The overall slope angle (OSA) is the angle measured from the lowest toe of the pit to the highest crest, including all benches, haul roads, and ramps within the slope profile.
- This angle gives a single measure of the steepness of the entire pit wall, accounting for the flattening effect of ramps and haul roads, which typically results in the overall slope angle being less steep than the interramp slope angle.
- The overall slope angle is essential for assessing the global stability of the pit and is a key parameter in mine planning and optimization, as it directly affects the pit’s footprint and the amount of waste that must be removed.
Key points
- The interramp slope angle is always steeper than the overall slope angle for the same pit wall, because the overall slope angle averages in the flatter sections created by ramps and haul roads.
- Both angles are critical for different aspects of pit design and stability analysis, and it is important to clearly distinguish between them in technical discussions and documentation.
In summary, the interramp slope angle focuses on the benched, ramp-free sections of the slope, while the overall slope angle measures the steepness of the entire pit wall, including all ramps and haul roads.
