Study And Application Of Digital Speckle Technique In Physical Similar Simulation Experiment Of Protective Layer Mining

For the coal and gas outburst of the mine,the protective layer of the most effective measures to eliminate one of the measures,The key to the study of protective layer mining of coal seam is the delineation of protection scope.Physical similarity simulation is an important method in the study of protective layer mining.The measurement of model deformation in physical similar simulation directly affects the reliability of the results.As a new type of modern optical measurement method,DIC has a full-field and non-contact advantage.In this paper,the digital speckle correlation method is analyzed theoretically and the interpolation algorithm is to improve the accuracy.The reliability of the method is verified by the laboratory test.Combined With the tilt Donglin's coal mining protecting strata engineering background,the DIC is used to study on deformation and protection range of overlying strata in protective layer mining The study results are as follows:(1)Based on the uniaxial compression deformation test of similar materials,the deformation and failure characteristics of displacement are studied by DIC.From two aspects of qualitative and quantitative validation of the digital speckle correlation method can be used in the similarity simulation experiment of protective layer mining.(2)The digital speckle pattern is introduced in the physical similarity simulation experiment of the lower protective layer mining.The comprehensive analysis of the roof displacement and the comprehensive analysis of the total strain are obtained by superimposing the contours of the overlying strata displacement contours and the plane total strain contours and the deformation maps of the overlying strata respectively;Based on the measurement of surface deformation of traditional physical similar model,a new method to analyze the deformation and failure law of overlying strata is proposed,which improves the measurement accuracy and perfects the research method of the roof rock movement law.(3)The distribution characteristics of the "ring nucleus" contours of the roof displacement cloud map and the plane total strain cloud map are determined,With the displacement "ring core" and the strain "ring core" as the "three bands" of the demarcation point to determine the height of the caving zone,the height of the fissure zone and the degree of eccentricity;The analysis shows that the upper part of the working face is within the range of 132.5mm and the range of fracture zone and collapse zone is 96.5mm,and the eccentricity is 0.117.(4)By using the digital speckle correlation method,the upper and lower boundary expansion and deformation angles of the protective range are 88 ° and 68 °,respectively,from the physical similarity model of the lower protective layer;Using the internal coal seam stress measurement method to obtain the protection range,the lower boundary pressure relief angle of 91 °,67.4 °;The results obtained by the two methods are similar,indicating that the protection range defined by this method is feasible.