The study of detecting method to the goaf areas in metal mines

There are a lot of underground goafs in most metal mines, which affect the safety of mining. To detect the underground goaf areas, some methods such as TEM, shallow seismic reflecting and seismic imaging are efficiently used in metal mines exploration. Through observing the attenuation changes of the secondary transient electromagnetic field time domain after interruption of power supply to distinguish the electric field distribution of different depths underground, by the resistivity changes of different measuring points to explain the geological formations change of different depths. The sampling points of the instrument must be increased to identify the deep target body. The transient electromagnetic method can find out multiplayer goaf in detecting the deep underground goaf areas. Shallow seismic reflection method is using artificial excitation source to vibrate particle near the vibration, forming seismic wave in the underground. At the interface of two different elastic medium, the reflection will happened. Using the intensity, frequency spectrum, phase position, wavelength and travel time of the reflected wave to judge the different medium and solve geological problems. Shallow seismic reflection method can delineate the boundaries of the goaf areas, it is suitable for various types of deep goaf areas, the depth of the goaf area can be calculated based on accurate wave velocity data. The effect is the best to find out goaf in the sedimentary rock area, but it is influenced by terrain. Seismic imaging method is developed based on the best offset from the reflected wave method. This method can use a variety of seismic waves as the significant wave to detect, according to the purpose of requirements it can also use only a particular seismic waves as the significant wave to detect. The main characteristic is the faster data acquisition, display more intuitive, as well as little limited by the filed, and additional correction is not needed in the data processing, which greatly saves the time of data processing. But the anti-interference ability is weak, the exploration depth is limited. The research group had used shallow seismic reflecting method and seismic imaging method to detect the goaf areas of the molybdenum mine at Luanchuan in Henan, and determined some goaf areas underground, the next work is using the transient electromagnetic method to identify the conclusion.