Detection And Radiation Law Of Natural Gamma Ray From Coal And Roof-rock In The Fully Mechanized Top Coal Caving Mining

It is well known that the key to realizing automation of fully-mechanized caving mining is automatic detection technology of coal and gangue, Therefore, the research about automatic detection of coal and gangue is the focus in field of fully mechanized caving mining technology which is concerned with further improvement on the technical level of full-mechanized caving mining and the guarantee of green mining and coal mine safety. Based on this, this paper combines with characteristics of hard and massive overlying strata applies theoretical analysis, site investigation, coal and rock sample on site and laboratory testing methods of combining for in-depth basic theory and technology of automatic detection of coal and gangue based on natural γ-ray.(1)The distribution characteristics of radionuclide in sedimentary coal and rock was research. The paper investigates and analyses the causes and distribution law of natural radionuclide in sedimentary coal and rock and get only three types of radionuclide including uranium and thorium which have effect on result of radioactive measurement. For coal mine roof, different sedimentary rocks have different radiation characteristics and the content of uranium, thorium and potassium make considerable difference too, radionuclide content of roof is related to the factors of the granularity of sediment, number of organic material in sedimentary, the sedimentary environment and conditions and deposition time. radionuclide content in the coal is much smaller than roof and can be ignored in the process of detection for which the gangue content of coal gangue mixture can be detected by radiation intensity from mixture of coal and gangue and detection process has a great advantage that detection process is not affected by the lumpiness of coal and gangue.(2)The test system about automatic detection of coal and gangue is manufactured. Designing and developing coal gangue mixed degree test bench, coal and gangue dynamic recognition system simulating process of caving and designing matching analyzing test system with independent intellectual property rights. Determining the reasonable exploration materials, performance and size can satisfy request of laboratory simulation environment about hydraulic support used for fully-mechanized caving. At the same time, detector parts model of the detection system are determined and the software of processing and display timely is developed forming the test system about automatic detection of coal and gangue used in fully-mechanized caving face.(3)The natural radiation model for mixture of coal and gangue and effective thickness for detecting were established. The saturated volume and the relationship between the radiation intensity and gangue content of coal and gangue mixture were calculated under different conditions. For statistical fluctuation law of radioactive count, the influence of background radiationwasanalyzed to low levels of gangue radiation detection process,the detection threshold, reasonable time and filter method of data were determined.(4) The intensity of the radiation detector detecting the gangue is related to the factors of the coal thickness covering on the gangue, the distance between gangue and detector, gangue weight, temperature, humidity and so on, the intensity of the radiation detector detecting the gangue has nonlinear relationship with the distance, different quality of gangue have different radiation intensity; when the temperature and humidity have a big change, it is necessary to install the temperature and humidity sensor to correct the probe detection value; the coal seam covering on the gangue has shielding effects on gangue radiation intensity, and if covering coal thickness increases, radiation intensity detected by gangue is reduced, thickness of 20 cm pieces of coal can shield the radiation intensity at the bottom of the gangue; For a mixture of coal and gangue, when mixed rate is less than 35%, radiation intensity increases with the increase in the mixed rate of coal and gangue, when mixed rate is more than 35%, radiation intensity increasing is no longer obvious with the increase of mixed rate.(5) Study from the paper: when the stable sampling period of natural radiation measurement system of coal and gangue is 0.1 second and filtering factor takes 20 with weighted moving average filtering method, it can satisfy the request in determining the tendency of the coal gangue in the coal waste mixture and displaying with real time. Through combined with theoretical analysis and testing in the laboratory, the paper analyzes the conditions and characteristics of applying natural γ-ray method for coal gangue detection experiment, determine index system and critical value of coal and gangue detection as well as determine the applicability of the natural γ-ray coal gangue automatic detecting technology.Research results lay a theoretical foundation for the field application about fully-mechanized coal gangue automatic detection.