Application Research Of High Density Electric Method And Transient Electromagnetic Method On Colliery Gob

In recent years,due to the endless mining and large-scale utilization of coal,a large amount of coal mining has drastically reduced the coal resources,leading to most of the coal mines have no coal to be mined and stopped mining coal and closed coal pits.Due to the lack of support and maintenance for a long time in mines and tunnels,tunnel subsidence and collapse will occur under the action of gravity for a long time,resulting in ground collapse and subsidence,and in serious cases,geological disasters will be caused,causing serious threat to the lives and properties of residents near the goaf.Therefore,it is a practical problem to clarify the details of goaf and provide necessary basic information for the management of goaf.In the exploration of goaf,geophysical method has been widely used because of its significant exploration effect.However,due to different terrain conditions,surrounding rock conditions,filling conditions,burial depth,etc.,the physical characteristics of different goafs are quite different.Therefore,it is reasonable to use different geophysical methods to detect and study the suitability of different goafs according to their physical differences on the basis.There are many geophysical methods to detect the goaf,such as audio magnetotelluric method,Radar method,seismic reflection method,controlled source audio frequency magnetotelluric method,high-density resistivity method,transient electromagnetic method,etc.Among them,the high-density electrical method is greatly affected by the terrain conditions,but its horizontal resolution is high,the transient electromagnetic method is almost not affected by the terrain,and the detection ability and effect of the filled coal mine goaf are good,but the reflection of high resistance is poor.Therefore,the main technical way to solve the harm of goaf is to study the effective geophysical exploration technology suitable for different physical properties of goaf.The main content of this paper is to study the application of high-density electrical method and transient electromagnetic method in goaf detection.Firstly,the basic principle of high-density electrical method and transient electromagnetic method,the advantages and disadvantages of different devices,method characteristics,data acquisition and processing are analyzed and studied,the physical characteristics of goaf are analyzed and compared,and the appropriate geophysical prospecting device is selected,and then verify through an instance.The high-density electrical method is studied by using numerical simulation software and five kinds of commonly used devices to carry out forward simulation technology for different sizes of geological abnormalies,and carry out inversion calculation and interpretation.Through comparative analysis of the numerical simulation results of different devices,the optimal device suitable for goaf detection is summarized.According to the one-dimensional forward program written by MATLAB software,the transient electromagnetic response characteristics of uniform and horizontal layered earth are studied by using the central loop device.From the study,the transient electromagnetic response curves are different in different geoelectric models.The general rule is that in the early transient electromagnetic response,high resistance is weaker than low resistance,and in the late transient electromagnetic response,high resistance is weaker than low resistance.And the transient electromagnetic response to the high resistance is significantly less than the low resistance,which reflects the low resistance information in the deep underground well.At the same time,the transient electromagnetic response characteristics of different device parameters under the condition of uniform half space are also different.The results of theoretical research are applied to practical engineering,and verified by examples,the high-density electrical method has a more obvious reflection on the shallow low resistivity anomaly,and can accurately reflect the location and depth information of the low resistivity anomaly.In the detection of the coal mine goaf,it can better reflect the distribution of the coal mine goaf and the reflection on the high resistance anomaly is greater than the actual goaf.When the gob is filled with water,the low resistance is obvious.Transient electromagnetic method is more sensitive to the low resistivity anomaly,and can detect the deeper target body.In the detection of the coal mine goaf,it can better reflect the distribution of the coal mine goaf,and the detection effect of the deep goaf is well.Therefore,the combination of the above two methods can effectively detect the goaf,and can find out the situation of the goaf from shallow to deep in detail.It provides a feasible basis for finding out the size,depth and resistivity characteristics of the goaf,which is conducive to the prevention and control in the later stage.