Exploration Technology Of Hidden Disaster Causing Factors By Underground Directional Drilling In Coal Mine

With the increase of coal mining scale,mining depth and mining complexity,the threat of safety production is becoming more and more serious.The major accidents are closely related with the hidden disaster-caused factors during coal mining,which caused the main safety accidents underground coal mine.Accident prevention is the primary means and work basis to ensure the safety of coal mine production,and the probability of disaster accidents can be actively reduced through the potential hidden-danger investigation and management.However,the exploration technology of hidden disaster-caused factors is at the stage of development,and the geophysical method has multiple solutions and needs to be explored during coal mining because of its short exploration distance,which affects coal mining and cannot be controlled.The conventional borehole was drilled without trajectory measurement and control,so it can't find the specific spatial location of hidden disaster-caused factors,and also exits exploration blind-spots,it is lagging far behind the need of advance exploration and management of large-scale mine.In this paper,the author proposed the program of the use of directional borehole for hidden disaster-caused factors from the need of the accident prevention and hidden disaster-caused factors exploration underground coal mine.By the use of experience,theoretical analysis,numerical simulation and field testing methods,aiming at the hidden disaster-caused factors connotation and identification characteristics,spatial location principle of hidden disaster-caused factors based on directional drilling,the influence factors and solutions of directional drilling trajectory measurement and control accuracy,formation identification with directional drilling based on natural gamma and resistivity,the following research is carried out on the following aspects.Detailed analyses of hidden disaster-caused factors such as gas,water damage,fire,roof,and rock burst were carried out,then goaf,fault,collapse column,coal seam stability;water filling source were selected as the main exploration,and the author studied definition,formation mechanism,classification and connotation of the exploration.From the aspects of spatial characteristics,lithologic characteristics and borehole characteristics,the different exploration points of the hidden disaster-caused factors were obtained,and the exploration criterion was constructed.According to different types of hidden disaster-caused factors,the structure form,the layout principle,the borehole structure and the detailed borehole design of trajectory parameter of the directional borehole were studied,in order to ensure that the directional borehole trajectory design was reasonable.Combined the description model of the directional borehole and the drilled stratum information with the coordinate system of mining engineering plane diagram,the coordinate figure exchange between two models were studied,the parameters of the control points and the precision in the space position of the coal seam were calculated,the real-time drawing of the contour line of the coal seam floor was achieved.The parameter acquisition method of common hidden disaster factors was deduced,and the influencing factors of the accuracy were analyzed,and the technical guarantee measures were given.Measurement and control accuracy of directional drilling was the main factor which affected the accuracy of hidden disaster-caused factors.The related factors of exploration directional borehole trajectory were studied with three aspects of calculation,measurement and control accuracy of borehole trajectory.The reason and calculation error about the borehole trajectory were analyzed,and the accurate spatial description of the borehole was achieved underground coal mine.Based on the principle of parameter measurement,the accurate measurement of borehole trajectory was realized by sensor optimization and software adjustment,and the influencing factors of measurement accuracy were analyzed,and the corresponding compensation calculation method was established.By comparing the signal transmission mode,the electromagnetic wave was selected as the signal transmission mode,and the electromagnetic wave transmission model was established underground coal mine,and the transmission characteristics and influencing factors of the electromagnetic wave were analyzed,the asymmetric dipole antenna was developed to realize the efficient transmission of the electromagnetic wave.After the wireless transmission signal of electromagnetic wave was transmitted to the orifice,by the use of the dual-channel data reception technology,and the signal processing method of amplification,filtering and decoding was used to realize the accurate demodulation of weak signal.Considering the effect of reverse torque and the deviation ability of directional drilling tools,the prediction method of drilling trajectory parameters at bit,the selection method of screw motor tool orientation angle and the selection method of deviation point were given.The accuracy of formation identification while drilling in directional drilling was the secondary factor which affected the accuracy of hidden disaster-caused factors.Formation identification method was developed based on the natural gamma and electrical resistivity,the measurement mechanism and measuring instruments were studied,calculation formula was given and the factors influencing the measurement was analysed,formation identification method was developed based on probabilistic neural networks(PNN),which provided the basis for hidden disaster-caused factors identification and directional drilling construction.The results were tested and applied in a number of coal mines in China,including fault and coal seam stability detection tests in Mengcun Coal Mine;the exploration experiment of goaf and water source in Baijigou Coal Mine;the exploration test of water source in the Meihuajing Coal Mine.Compared with the traditional exploration method,the precision of directional borehole was high,the distance was short,the period was short,and the hidden disaster-caused factors can be governed,and the remarkable application effect was achieved,which provided a new technical means for disaster prevention and control underground coal mine.