Direct block scheduling technology : analysis of avidity.

This study is focused on Direct Block Scheduling testing (Direct Multi-Period Scheduling methodology) which schedules mine production considering the correct discount factor of each mining block, resulting in the final pit. Each block is analyzed individually in order to define the best target period. This methodology presents an improvement of the classical methodology derived from Lerchs-Grossmann?s initial proposition improved by Whittle. This paper presents the differences between these methodologies, specially focused on the algorithms? avidity. Avidity is classically defined by the voracious search algorithms, whereupon some of the most famous greedy algorithms are Branch and Bound, Brutal Force and Randomized. Strategies based on heuristics can accentuate the voracity of the optimizer system. The applied algorithm use simulated annealing combined with Tabu Search. The most avid algorithm can select the most profitable blocks in early periods, leading to higher present value in the first periods of mine operation. The application of discount factors to blocks on the Lerchs-Grossmann?s final pit has an accentuated effect with time, and this effect may make blocks scheduled for the end of the mine life unfeasible, representing a trend to a decrease in reported reserves

Assessing and controlling of bench blasting-induced vibrations to minimize impacts to a neighboring community.

Blasting is an important operation in mining production but is a source of concern due to its associated environmental impact; in particular, blasting-induced vibrations may cause structural damage and human discomfort. For decades, communities near open-pit mines have complained of blasting-induced vibrations. This study presents a methodology to predict, assess, and control ground vibrations in large open-pit mines operating close to a community. To conduct this study, 178 levels of blastinginduced vibrations were recorded in an area encompassing a large open-pit iron ore mine and a neighboring community located in the Quadril atero Ferr?fero, state of Minas Gerais, Brazil. Collected data were processed with multiple regression techniques to obtain the blasting vibration attenuation law to predict the levels of blasting-induced vibrations for the locality studied with knowledge of only the maximum explosive charge per delay and the distance to the blasting point. Brazilian and international admissibility standards of blasting-induced vibration, the minimum distance between the mine and community and the constants obtained from the regression were used to establish the maximum explosive charge per delay for an acceptable ground vibration level that would not cause structural damage and human discomfort. Finally, the proposed methodology was validated by comparing the predicted ground vibrations levels to measured values. The results demonstrate that this methodology can be applied to any open-pit mine to control blasting-induced vibration effects

Analysis of the impacts of slope angle variation on slope stability and NPV via two different final pit definition techniques.

The traditionally and widely used Lerchs-Grossmann algorithm presents well-known limitations that newer propositions attempt to overcome. The direct block schedule (DBS) methodology, which has gained relevance with computational advances, obtains the final pit as a natural result of production sequencing, different from Lerchs-Grossmann-based algorithms. This process flow applies constraints in the final pit definition stage attempting to provide a more realistic result and to minimize risks. Slope instability is a common and inherent risk to open pit mining and may affect the project's net present value (NPV). A study of the impacts of slope angle variations on safety indexes and final pit NPV provides an auxiliary tool for the overall slope angle definition process. This article presents a case study in which the effects of variations of the overall slope angle on the safety factor (SF) and project NPV were analyzed. A total of 25 pits were generated by each studied final pit definition methodology, and each pit had the sections with the varied slope angles analyzed in the stability assessment, resulting in a total of 150 slopes analyzed. A comparison between the results obtained by the two different methodologies implemented in commercial software is presented. The results show no relationship between the NPV and the overall slope angle using the DBS methodology. An analysis of the results for each geotechnical sector obtained by the traditional methodology was conducted and may contribute to the trade-off analysis between the best slope angle to achieve a reasonable SF and the maximum NPV