BLOCK CAVING (Hundimiento por Bloques)
Block Caving Method Tutorial
Introduction to Block Caving
- The block caving method is a mining technique that falls under unsupported and subsidence methods, where extracted material collapses due to gravity.
- This method involves creating cuts at the base of the deposit to induce material collapse, allowing for efficient extraction.
Characteristics of Block Caving
- Unlike other mining methods, block caving does not use pillars for support; it relies on drilling and blasting techniques. This results in lower operational costs compared to traditional methods.
- The process creates void spaces that facilitate the upward movement of fragmented material after extraction.
Application Criteria
- Block caving is applicable when deposits have a dip greater than 70 degrees and are tabular in shape with competent rock types (3a to 4a). A regular rock mass rating (RMR) between 31 and 40 is ideal.
- It is particularly effective for large-scale deposits but less suitable for smaller or low-grade deposits due to its high production capacity requirements.
Advantages of Block Caving
- The method offers a low cost per ton mined, making it economically favorable for large operations with significant mineral volumes. Additionally, it can extract low-grade copper ores effectively.
- Automation potential and low accident rates are notable benefits, along with minimal drilling and blasting needs compared to other methods like panel caving used in primary ore bodies.
Disadvantages of Block Caving
- A major drawback includes dilution rates ranging from 30% to 40%, as surrounding waste rock may mix with the ore during extraction processes. This necessitates careful management of materials during operations.
- Significant initial investment is required for preparatory works before accessing mineral deposits, which can lead to extended timelines before actual mining begins (e.g., projects like those at Codelco).
Conclusion on Operational Costs
- When comparing operational costs per ton across various mining methods, block caving stands out as one of the most economical options if certain conditions regarding deposit size and depth are met (minimum depth around 100m). Average production rates can range from 10,000 to 100,000 tons per day depending on these factors.
Extraction Point Spacing and Rock Quality
Extraction Point Specifications
- Discusses the maximum and minimum spacing between extraction points, emphasizing that for a 3-meter extraction point width in class 3 rock, the distance should be a maximum of 18 meters and a minimum of 10 meters.
- Highlights the importance of determining the diameter of the ellipse based on rock quality and extraction points.
Mining Methodologies
- Introduces the Nicolas method as an effective technique, mentioning its application in blue caving to achieve higher values.
- Recommends that mineral thickness should exceed 100 meters for optimal scoring, with an inclination greater than 55 grams; uniform distribution of grades is also advised.
Rock Matrix Resistance
- Suggests that weak rock quality is preferable, with high fracture spacing and low sealing resistance for both hanging walls and footwalls.
- Explains how these characteristics contribute to achieving higher scores in mining assessments using the Nicolas method.
Autocad Model Overview
Production Levels and Block Models
- Describes a schematic created in Autocad showing production levels, block models under preparation, and areas where drilling has commenced.
- Details labor areas where drilling occurs transparently through intersecting levels for ascending perforations.
Mineral Transport Process
- Illustrates how mined material is transported via a shaft (Pique), loaded onto trucks for commercialization after blasting operations are completed.
Designing Mining Methods
Considerations for Effective Design
- Emphasizes that designing an effective mining method requires careful consideration of various factors including rock type and adherence to regulations such as Supreme Decree 023.