Experimental Study On Overlying Strata Deformation Based On DIC

Monitoring overburden deformation caused by coal mining is an important part of coal mine safety and green mining.Quantitative description of mining-induced overburden migration and fracture development is a key scientific problem for accurate coal mining.Digital image correlation method has the characteristics of high precision,non-contact and real-time,which is helpful to realize the detection of rock deformation in a wide range and multiple scales.It is one of the effective ways to promote the informatization,digitalization and visualization of coal mining to carry out the research of digital image correlation detection of overburden deformation and fracture development.This article in view of the mining strata deformation detection of digital image correlation method,based on the physical model test,combined with theoretical analysis,the theory of digital image correlation method,method of digital image correlation detection system,the optimization of speckle pattern,the selection of calculation parameters and macro mesoscopic deformation detection and characterization of similar model and other issues were studied.The theory of digital image correlation method is analyzed.According to the theory and experiment,this paper analyzes the error that may appear when using the digital image correlation technology in the process of similar model test,improves the test system layout,operation process,data analysis and so on,and improves the measurement accuracy.The speckle pattern and the parameters of the simulation test were optimized.According to the different requirements of similar material model experiment,the technology of speckle making,key parameters and pattern quality were studied.Combined with the experimental verification,the method of making high-quality speckle pattern is given,and the problem of making high-quality speckle pattern on the surface of standard specimen and similar model is solved.The influence mechanism of DIC calculation parameters on the measurement results was studied.Taking the quality of speckle pattern and the non-uniform deformation of the model into consideration,a two-parameter threshold method for sub-region size selection was proposed,and the effectiveness of the method was verified by experiments.A two-dimensional model test of overburden deformation was carried out,and the digital image correlation method for detecting and characterizing the macroscopic and microscopic deformation of strata was studied.This paper reveals the relation and failure law of macroscopic and microscopic deformation of rock strata,and defines the criterion for determining the occurrence of separation fractures on the microscopic scale.It is shown that the crack development length is closely related to the length of strain localized zone,and the crack development length can be quickly estimated according to the length of strain localized zone,so as to predict the failure pattern of roof.The surface strain field of the model was acquired by digital image correlation method,and then the measuring lines were placed in the strain localization zone to obtain the macroscopic and microscopic fracture opening degree and length,which were compared with the synchronous measurement data of the total station,and the maximum relative error was 7.73%.The test verifies the correctness of the digital image correlation method for detecting and characterizing macroscopic and microscopic deformation and failure of rock strata.