Study On Key Techniques Of Overburden Failure Detection By Direct Current Method

With the development of coal mining,the roof overburden produces caving zone and water conducting fracture zone,and the floor overburden produces failure and deformation.If the fracture develops to the hidden aquifer near the coal seam,it will lead to water inrush accident.Therefore,the research of overburden failure detection technology is of great significance.The damage of overburden rock will lead to obvious changes in its electrical properties.The geoelectric field method is applied to study the overburden damage,which is pertinent.In this paper,the response of all-space apparent resistivity method,borehole apparent resistivity advance detection and natural potential method in overburden failure detection are studied respectively,and three methods are synthesized to detect overburden failure and development,providing technical basis for coal mine safety production.By studying the law of the change of resistivity and the empirical formula of the failure zone under the overburden failure,the geoelectric model of overburden damage with different roof lithology,different mining thickness and different mining stages is established,and the forward modeling is obtained: At different stages,the apparent resistivity of the model increases correspondingly,in which the resistivity of the sag zone can be increased to 4 times(with sandstone as the background),and the resistivity of the water-conducting fracture zone is increased to 11 times(with mudstone as the background).In combination with engineering research,the apparent resistivity of the falen belt is increased by 6 times(with mudstone as the background).A borehole full-space electrical advanced exploration model is established,and the position of anomalous body is changed for forward simulation.After comparing the simulated resistivity extremum position with the anomalous setting position,the linear coefficient range of advanced exploration is 0.1-0.33.The linear coefficients obtained from the field experiments of borehole ful-space electrical advanced exploration ranged from 0.14 to 0.34.The range of linear coefficients obtained from numerical simulation and field experiments is mutually corroborated.Combining with engineering research,the advance detection method of drilling lithology self-training is put forward.The advance detection range is adjusted by using the linear coefficient of self-training,which solves the engineering problem that the vertical control height of drilling hole is insufficient and the fracture zone outside the hole can not be detected.Studying the form solution of spontaneous potential,it is recognized that the overburden fracture leads to the change of resistivity gradient and consequently the change of spontaneous potential.Natural seepage spontaneous potential monitoring experiment shows that spontaneous potential decreases as a whole when seepage occurs and restores to its original state at the end of seepage,which proves that spontaneous potential is controlled by lithologic resistivity and has the ability to reflect fracture seepage.The method of collecting,processing and analyzing SP data in the process of engineering monitoring is put forward,and the overburden failure state is evaluated by SP method.In this paper,the key technologies of overburden failure detection by direct current method are studied by numerical simulation,field experiments and engineering examples.The results show that: firstly,apparent resistivity technology is used to preliminarily detect the development height of the failure zone.If the vertical control height of boreholes is lower than the development height of the failure zone,the fullspace electrical advanced detection technology is used to supplement the detection,and finally,self-detection is used.The overburden failure and seepage can be judged by the natural potential method,and the overburden failure can be monitored by three methods for a long time.The process of overburden failure can be judged accurately,and the roof and floor water disaster accident can be predicted and predicted effectively.There are 66 maps,13 tables and 94 references in the thesis.