Tem Response Characteristics Of Multi-layer Mined Out Area In Coal Mine

Coal is an important part of China’s energy structure.With the increasing demand for coal resources,coal mining depth and mining intensity,speed and scale of mining have been improved,so a variety of complex goaf such as single or double layers have been arising,therefore,It is of great significance to find out the location and the existing form of the mined out area.Based on the study of the electrical properties of goaf,with the help of Maxwell software the paper had established six fixed depth and resistivity one-dimensional goaf geoelectric model including low resistivity of monolayer,high resistivity of monolayer,low resistivity of bilayer,high resistivity of bilayer,low and high resistivity of bilayer(low resistivity in the upper,high resistivity in the lower)and high and low resistivity of bilayer(high resistivity in the upper and low resistivity in the lower).Through arranging wire frame of different sizes above themodel,and using Maxwell software for forward calculation,and analysing of voltage decay curves of different models,we can see that the initial value of normalized voltage response is low resistivity of monolayer>low and high resistivity of bilayer>low resistivity of bilayer>high and low resistivity of bilayer>high resistivity of monolayer>high resistivity of bilayer,the initial response voltage value of low resistivity of monolayer is the largest,and the initial response voltage value of high resistivity of bilayer is the lowest.Results from comparison voltage attenuation curve of the different mode and of homogeneous half space under different sizes of wire frame,the best transmitter loop of single layer model is 120 m * 120 m under the fixed depth,the best transmitter loop of double layer model is 150 m * 150 m.In this paper,the single and double goaf respectively had established the three-dimensional model,and focus on the analysis of several models of multi-channel voltage diagram,results show that the influence range of abnormal body in low resistivity of monolayer model in the horizontal direction can reach abnormal body boundary’s 80m;in survey line position of parallel to the abnormal body,influence range can reach the abnormal body boundary’s 60 m.The influence range of abnormal body in low resistivity of bilayer model and low and high resistivity of bilayer model in the horizontal direction can reach abnormal body boundary’s80m;in survey line position of parallel to the abnormal body,influence range can reach the abnormal body boundary’s 80 m.When the model is high low resistivity of bilayer,voltage values of the survey line above abnormal body did not change significantly,but compared to the value of voltage response in homogeneous half space,it is higher,and influence range of abnormal body in the horizontal direction can reach abnormalbody boundary’s 40m;in survey line position of parallel to the abnormal body,the range of the influence of the abnormal body boundary is not well certained.The results show that the facts of the situation are in accord with the simulation results,and the correctness of the simulation is proved in a coal mine in Changzhi.