Research On 3D Direct Current Survey Of Working Face Floor Crossing Holes

With the gradual transformation of coal mining into deep-seated development in China and the complex and changeable of deep geological conditions,mine water hazards caused by water inrush from the floor of the working face happened from time to time,so it is particularly important to detect the water content of the floor stratabefore mining.Among many geophysical prospecting methods for mine water management,mine direct current resistivity method has been widely used because of its unique advantage of high sensitivity to water body,which is based on the differences of conductivity between rock and ore body.A great deal of work has been done on the researches and applications of mine direct current method.On the basis of previous studies,this paper applies the cross-hole direct current method into the research of underground water management.In combination of the advantages of the cross-hole method in detection accuracy and resolution,the data collected by the ultrahigh density electrical method system,the utilization of the limited space of the mine and the rational arrangement of exploration bore holes,the three-dimensional full-space layout of the working face floor thereby can come ture.Through numerical and physical simulation calculations,the response characteristics of this detection method to the abnormal body of the working face floor can be analyzed that provides a new solution for the mine water management.Firstly,this paper summarizes the present research status and achievements of mine direct current methods and cross-hole imaging technology and further introduces the related conceptions of direct current resistivity method and the acquisition method of cross-hole resistivity.Based on finite difference forward numerical simulation and smooth least squares inversion method,anomalous body models(block,cylinder and flat)are established using crosshole bipolar device(A-M),three-stage device(AM-N),dipole device(AB-MN)and differential device(AM-NB)to simulate and collect data,respectively.The advantages and disadvantages of different device types are studied by analyzing the slices obtained from data processing of the established geological model from different angles.The simulation results show that the differential device(AM-BN)can not only achieve the requirement of "perspective-topenetration" stereoscopic observations,but also has significant advantages in signal strength and spatial resolution in comparision of three other devices.The low resistance and high resistance anomalies all show good anomalous responses in resistivity three-dimensional slices and the low resistance anomaly response is even more obviously.The feasibility of cross-hole DC method for this detection result is theoretically obtained.In terms of the principle of similarity,models of the flume physical are established within the tap water to calculate the environment of the surrounding rocks,Typical anomalous bodies used for modeling are selected as iron blocks,iron prop and discus,respectively.Data acquisition is carried out by differential device(AM-BN)that provides better detection effect in numerical simulation.The experiment shows that the results obtained by modeling illustrate a certain extent of anomalous phenomena in three-dimensional resistivity slice maps.The results of numerical simulation are essentially in agreement with reality that implies the effectiveness of this detection method for anomalous body detection.