A zero-one integer programming model for open pit mining sequences

The open pit mine production scheduling can be defined as: Specifying the sequence of block extraction from the mine to give the highest NPV, subject to a variety of production, grade blending and pit slope constraints. Production scheduling over a certain period is known as the scheduling horizon. Production scheduling typically encompasses three time ranges for decision making: longterm, medium-term and short-term. Long-term can range from 20 to 30 years depending on the situation. The 20 to 30 year periods are broken into several smaller periods with a duration between one and five years. A medium-term schedule ranges from one to five years, which gives more detailed information, allowing for more accurate design such as extracting from a special area of a mine, substituting the equipment and purchasing of the needed resource capacities. The one to five year period is broken into one to six month periods for more detailed scheduling in the intermediate-term model. Finally, short-term production planning duration is between one month and one year. Similarly, this period is divided into daily, weekly or monthly subperiods. During short-term scheduling, detailed design of the mine takes place and the long-term plans, typically annual plans, are implemented on a level of detail suitable for guiding operations in a time frame that meets the needs of production planning at the mine. At this level of design, the goals are: ➤ Properly utilize production equipment by avoiding idle time and excessive moves to different working levels ➤ Ensure that stripping proceeds in advance of ore production ➤ Maintain working slope angles ➤ Provide haul road access to all working benches ➤ Maintain ore blend to avoid excessive quality and quantity fluctuations at the mill ➤ Minimum deviation from the long-term and medium-term plans ➤ To ensure a production schedule that is practical in terms of mining operations ➤ To ensure maximal flexibility of the system. When a non-homogeneous deposit is to be mined, a detailed short-term production schedule becomes a necessity in order to provide a homogeneous concentrator feed. If the deposit is extremely non-homogeneous, blending facilities are usual required between the mine and concentrator. Because of the very short time usually available for short-term production scheduling, it is nearly impossible to consider all factors in a manual scheduling method. Also, a quick revision of the production schedule under emergency conditions, such as a breakdown of a shovel or unexpected changes in the ore grade, is impossible in this method. Therefore, the mathematical programming method, such A zero-one integer programming model for open pit mining sequences