Study Of Coal-Rock Characteristics Identification Method Based On GPR And ESR

Underground intelligent and unmanned coal mining technology is the future development goal of China's coal industy.The key technological breakthrough areas identified in the 12th Five-Year Plan of National Energy Science and Technology?2011-2015?include unmanned mining technology.It is pointed out that it is necessary to focus on the automatic identification technology of coal-rock characters and so on.The 13th Five-Year Plan for Safety production in Coal Mine?2016-2020?clearly pointed out promote the automation,informatization and intelligent transformation of coal mine mechanization,and gradually realize the coal mine underground no-man working face.In addition,the National key basic research program?973 Plan??2014-2018?"the key basic research of unmanned mining in deep dangerous coal seam",which regards"the principle and realization method of on-line identification of coal and rock characters and the perception of mining state"as a key sub-subject.It is pointed out that on-line identification of coal and rock properties is the most important information basis for realizing autonomous control of unmanned mining equipment in deep coal seam,and is the basis for realizing automatic height adjustment of shearer drum.Therefore,it is of great significance to study the identification of coal-rock interface for realizing intelligent and unmanned coal mining in fully mechanized mining face.Coal-rock identification has always been a research hotspot,although many scholars at home and abroad have put forward a large number of solutions,but these methods basically stay in the feasibility of the method.At the stage of discussion,there is no effective solution to study the characteristics of coal and rock.In this paper,taking coal-rock medium as the research object,taking the electromagnetic characteristics and the free radical characteristic parameter difference of coal-rock as the research contents,the related research on coal-rock character identification is carried out by using electromagnetic wave technology,and the following work is completed.?1?Taking the coal-rock interface as the research object,the coal-rock interface model with electromagnetic parameters is constructed according to the characteristics of coal-rock geological occurrence conditions,and the method and applicability of coal-rock interface identification based on electromagnetic wave technology are explored.According to the three-layer scattering model of coal-rock interface,taking into account the difference between coal and rock electrical properties and the attenuation characteristics of electromagnetic wave propagation,the geological radar equation of coal-rock interface is established,which provides theoretical support for GPR detection of coal-rock interface.It also provides the basis for antenna selection.Different coal-rock combination have been carried out.The applicability of electromagnetic detection under different frequency of GPR antenna and different geological conditions is studied in this paper.Considering the complex variability of coal mine geology,the finite difference time domain method?FDTD?is used for numerical simulation,and the geometric models of different frequencies,different dielectric constants and different coal-rock combinations are established.The applicability of geological radar to detect the coal-rock interface is analyzed by forward numerical simulation.Finally,combined with the field environment of coal mine,the LTD-2100 radar is used to verify the underground physical experiment,and the experimental results are explained.The results show that the GPR system can satisfy the application of the vast majority of coal and rock interface identification.In practical application,the detection of coal rock interface can be realized by means of ground penetrating radar moving with coal worker,or advanced exploration can be adopted.?2?The parameters of ESR absorption spectrum of different kinds of coal and rock media were extracted,and the industrial analysis and X-ray Fluorescence?XRF?analysis of coal and rock samples were carried out.Based on the analysis of the key parameters of ESR absorption spectrum of coal and rock,such as Langde factor g,line width?H,line height h and free radical concentration Ng,the mechanism of free radical change of different kinds of coal and rock is established.The feasibility of using X-band electron spin resonance spectrometer to detect the free radicals of coal and rock is preliminarily verified.Through the analysis of absorption spectrum parameters,it can be concluded that the value of g factor is between 2.002 and 2.003,and the value of g factor with the increase of coal rank,showing a decreasing trend.Especially,the g value of the two sandstones is lower than that of lignite,but larger than other bituminous coal and anthracite,and the change of g value is related to the kinds of free radicals and impurity atoms.A preliminary conclusion can be drawn as follows:small molecular free radical g value>macromolecular free radical g value.By analyzing the ESR linewidth of different kinds of coal and rock samples,it can be concluded that with the increase of coal rank,the linewidth of free radical becomes narrower.The linewidth variation of the two sandstones is small,but higher than anthracite and lean coal,smaller than coking coal.It can also be concluded that the free baseline width of small molecules is larger than that of macromolecules.According to the Ng analyzer of free radical concentration of different kinds of coal and rock samples,the free radical concentration increases with the increasing of the degree of fragmentation and the increasing of the free radical concentration of the coal rank.?3?An improved maximum inter-class variance algorithm?IOTSU?for GPR image recognition of coal-rock interface is proposed.The traditional OTSU algorithm only considers the inter-class variance of the object and background.The classification information contained in each class is not taken into account,and in order to make the coal-rock interface recognition more accurate in GPR images,it should also consider the minimum pixel distance within the class,so we present the minimum intra-class variance:D_inner?7?s,t?8?,the smaller the value,the better the intra-class pixel cohesion of the background and target.By changing the threshold?s,t?enableD_inner?7?s,t?8?gets the minimum value.Therefore,combined with the maximum inter-class variance and the minimum intra-class variance,an improved IOTSU algorithm is proposed in this paper.The threshold selection index is as follows:?37?_s?7?s,t?8??28?D?7?s,t?8?/D_inner?7?s,t?8?.When _s?37??7?s,t?8?gets the maximum?s,t?,the value is the optimal threshold for two-dimensional segmentation.The experimental results show that the method proposed in this paper can effectively improve the recognition accuracy of coal-rock interface,the accuracy of classification and recognition can reach 96.3%,and it also has a strong adaptability.?4?Based on the difference of free radical ESR character of coal and rock,a coal-rock identification method based on ESR-SVM-CID is proposed,which solves the problem of coal-rock identification with similar coal-rock characteristics or no radioactive elements of sandstone.The main characteristic parameters of the ESR absorption spectrum of 100 groups of different coal and rock media were extracted,as the characteristic data set,and the original data were pre-processed.Then the classification model is established by SVM,and the classification test is carried out.The experimental results show that the classification accuracy of coal and rock media can reach 100%.The accuracy of four classification of different coal types and rocks can also reach 100%,and the accuracy of classification of different bituminous coals can reach 83.3%according to high,middle and low grade bituminous coals.In addition,ESR-SVM method can also be used to identify complex coal seams which contain gangue,and the accuracy of classification can reach 100%.The results show that the ESR-SVM-CGID coal-rock identification method proposed in this paper can not only identify different coal-rock media under the condition of similar electrical parameters of coal-rock,but also have a good universality.In addition,it can also be used as an effective method for coal classification and detection.The method does not directly give the coal-rock interface information,but the effective identification of the coal-rock medium can be used as a judgment basis for judging the cut-off state of the coal-mining machine?coal-cutting/rock-cutting?and indirectly reach the purpose of identifying the coal-rock interface,so as to provide a criterion for automatic height-up of the drum of the coal mining machine.