Data Acquisition And Processing Of Mining Subsidence Model Experiment Based On Digital Photography

Mining subsidence is one of the main forms of mining damage,and similar material model test is an important technique to study mining subsidence mechanism and surface deformation law.In the model test,the displacement information is measured by means of setting observation point mark to reveal the mining subsidence rule.Therefore,it is of great significance for similar material model test to improve the accuracy and efficiency of displacement measurement.The deformation monitoring based on similar material model has the characteristics of small range,high precision and timeliness,however,the conventional model monitoring method has some limitations in measuring precision and efficiency.(1)Theoretical knowledge of displacement monitoring based on digital camera are introduced,which is an important contents supporting close-range photogrammetry data processing.In recent years,three-dimensional laser scanning and digital close-range photogrammetry system has been successfully applied to the model test,but these methods need to use the big special equipment with complex operation and high cost,which are not convenient for popularization and application.For this purpose,this paper discusses the displacement observation of the model measuring points with ordinary digital camera method.Control grids are laid around every observation point and fixed in the model frame.In the test,the coordinates of every observation point relative to the control grid are calculated after image coordinate transformation and geometric distortion correction of pictures with observation points and control grid taken by common digital camera to realize high precision gathering and processing about the model test data of mining subsidence.Aiming at the characteristics and monitoring accuracy requirement of similar material model test about mining subsidence,this paper discussed a reasonable solution to layout monitoring points and control grid,including the material of monitoring point symbol,the distance among points,the size of control grid,the dividing and fixed way of the grid.Based on the theory of photogrammetry,the relationship between the focal length,pixel,photography distance and image resolution of digital camera are analyzed,and the influence factors of image point coordinate precision of digital photographs are discussed.The hardware used for external photography was determined according to the specific conditions of the test model.In view of the characteristics of the grid type dense distribution of the image control points in this digital image,the finite element model is used to calibrate the system error of the plane distortion,and the aberration difference of the image points is inserted in the first spline function to compensate the aberration difference of the image points.Finally,the constraint conditions are added to the accuracy of the distortion correction.A set of model experiment data processing system is developed,which can realize the high precision solution and visualization of the coordinates of the model point.At the same time,based on the geological mining conditions of 8211 working face of Yanjiahe coal mine,the mining subsidence test model was made,and the test data were collected and processed using above methods.The test result shows that the data gathering and processing system for mining subsidence model based on ordinary digital camera is simple and practical,and the precision of measuring points'coordinates gained by the system satisfies the requirement of model test.The system has popularization and application value.