Study On The Mechanism And Technology Of Advanced Detection With Transient Electromagnetic Method For Roadway Drivage Face

Buried water conducting passages and water-bearing structures before the roadway drivage face may easily lead to water bursts in coal mines, greatly affecting the safety and efficiency in coal mine production. The development of a new geophysical technology to detect buried water conducting passages and to predict water-bearing structures accurately and instantaneously is of great operational importance. For its many advantages, such as rapid and convenient operation, long detection distance, the advanced detection technology with transient electromagnetic method has been applied in many coal mines of China, but study on its basic principle is not enough. A synthetically study means combined with numerical simulation, physical modeling and practical application is applied to study the mechanism and technology of advanced detection with transient electromagnetic method. The achievements and innovations as following:(1) According to the geoelectric characters of the coal-bearing strata and the transient electromagnetic advanced detecting method, the concept, that the exciting direction is perpendicular to the stratum and parallel to the stratum in whole space, was proposed;(2) Based on the diffusion equations of the electromagnetic field, the 2.5D finite-difference time-domain (FDTD) equations were established, the exciting source setting in the wave-number space domain was solved by the cosine filtering, the FDTD program was designed for the whole space transient electromagnetic field;(3) Using the FDTD program, the whole space transient electromagnetic field diffusion process was simulated that the exciting direction is parallel to the stratum, so is done that the exciting direction is perpendicular to the stratum, the response characters of different geoelectric sections were drawn, the response of the fault and the fallen-column was studied and the mechanism of advanced detection with transient electromagnetic method was revealed;(4) The experiment system used to simulate the advanced detection with transient electromagnetic method in roadway space was designed independently, different geologic structures were simulated and the response of abnormal bodies was gained;(5) According to the test in mine, the disturbing of the road heading machinery was analyzed; the distance out of its influence was given.