Research on the application of time shifting aeromagnetic method in detecting coal mine burning areas

Abstract

The spontaneous combustion of coal seams leads to the formation of magnetic minerals in the overlying strata, exhibiting high magnetic anomaly features, providing a physical prerequisite for the magnetic method to detect the burning area. The aeromagnetic method has achieved good results in detecting coal mine burning areas, but it cannot effectively detect the development trend of coal mine burning areas. In order to solve the above problems, based on the aeromagnetic method method, a time-shifting aeromagnetic method is proposed. It involves conducting two aeromagnetic detections within a certain time interval. Based on the difference between the two aeromagnetic inversion results, the features of the coal mine burning area over time are determined. It achieves the goal of effectively detecting the distribution range and development trend of the coal mine burning area. In order to balance the terrain fitting effect and inversion calculation efficiency in undulating areas, a composite mesh generation method of regular and irregular grids is adopted. The tetrahedral irregular grid generation is used in undulating areas on the surface, and hexahedral regular grid generation is used in areas below the surface. The results show that the regular and irregular composite mesh generation method not only meets the requirements for inversion precision under undulating terrain conditions, but also improves the inversion calculation efficiency by nearly 6 times compared to the tetrahedral irregular mesh generation method. A numerical model is established based on actual geological conditions. The actual testing is conducted using unmanned aerial vehicles and aviation optical pump magnetometers. The numerical simulation and actual measurement results indicate that the time-shifting aeromagnetic method can accurately detect the distribution range of burning areas and the development trend of burning areas over time. It provides a basis for carrying out fire prevention and extinguishing work in coal mines.

Keywords

• coal spontaneous combustion
• burning area
• time-shifting aeromagnetic method
• mesh generation
• magnetic anomaly inversion