Mapping collapsed columns in coal mines utilizing Microtremor Survey Methods
利用微动勘察方法探测煤矿陷落柱

Collapsed columns post one of the deadly safety risks to coal miners. Therefore, how to effectively map collapsed columns has become an urgent business matter for improving coal mine safety and coal production. This article documents the first application of the microtremor survey method to map geological hazards in the coal mining areas. Our results demonstrated the usefulness and effectiveness of the method, primarily due to the sensitivity of shear waves to the low-velocity collapsed columns. In the 2002 working region within the Shanxi Lu'an Zhangcun coal mine area, both the S-wave velocity structure inverted using the simple-point inversion method and the apparent S-wave velocity (vx) section obtained using the 2D microtremor profiling method clearly display the known collapsed columns. The collapsed column positions displayed in the 2D microtremor section are consistent with those seen from the tunnel, having a boundary error approximately 10 m. The microtremor method has been proved a very effective and useful geophysical tool to improve coal mining safety, because of the following characteristics: (1) high resolution, (2) no need of using the artificial source, (3) convenient and low-cost field data acquisition, and (4) little effect from local cultural structures. The microtremor survey method is also technically superior to any other geophysical method in detecting or mapping these low or high S-wave velocity anomalies. Therefore, it has a bright future in many geological and geophysical applications, such as investigation of coal seam structures and collapsed columns underneath villages.