3-D Stable Current Field Distribution Analysis And Advanced Prediction Research In Mine

The direct current(DC) resistivity advanced detection in mines is a kind of geophysical prospecting method used to predict potential disasters(water hazards) ahead the excavated work face, which has many advantages, such as economical, convenient, high-efficiency and so on, however, in the aspect of theory, it is immature. In this paper, roadway influence and several typical models are studied by means of finite element numerical simulation method.Firstly, the concept of roadway influence factor is introduced so as to study the relationship between roadway influence and roadway geometric size, power source position, conductivity of surrounding rock and device types. The results show that the existence of roadway cavity changes the distribution of stable current field, especially around the face of the roadway. However, as the electrodes distance increases, roadway influence decreases significantly and when electrodes distance increases to a certain value, the roadway influence can be neglected. Dipole device and three-pole device are adopted respectively, and it is found that the roadway influence degree of these two kinds of devices only has slight differences. Then change the roadway geometric size, it turns out that as the roadway geometric size becomes larger, the influence on the distribution of the current field becomes more serious. If single pole device is applied and the power source is placed at 0 meters,4 meters and 8 meters ahead of the roadway face respectively, it comes out that when the power source is at the roadway face (0 meters), the roadway influence is the most serious, while at the other two positions, roadway influences are relatively weak and they are almost consistent. If the resistivity of surrounding rock is lower compared with its adjacent layers, then the greater the difference in conductivity between surrounding rock and its adjacent layers is, the smaller the roadway influence becomes. However, if the resistivity of surrounding rock is higher than its adjacent layers, the result is just the opposite.Layered models are designed to study the distribution characteristics of the current field and on this basis, typical geoelectric models are simulated and analysed. The results show that the distribution characteristics of current field in whole space are related with electric conduct differences between layers and the thickness of each layer. The abnormal characteristics of the collapse columns and fault not only involve with electric conductivity differences between layers and the thickness of each layer, but also has something to do with anomalous body's conductivity, size, shape and the distance to the roadway face. The relationship between the distance to the roadway face and the abnormal characteristic of current field(the extreme value point's position of apparent resistivity curve) is analysed and the equation of them is got. Finally, the observed data is analyzed and processed. Then, based on the geological and mining drilling logging data, a layered geoelectric model is designed, through multiple modifying the parameters of the model to achieve the purpose of the forward simulation fitting inversion. At last, according to the best fitting, we can determine the position of anomalous body.