Study On Rupture Mechanism And Damage Characteristics Of Loose Coal Rock

Most of the coal mine dynamic disasters are related to the stability of coal and rock,and the stability of coal rock is closely related to its mechanical properties.The properties of soft coal and rock are quite different from other coal rocks,so the mechanical properties of soft coal rock can be studied.It is of great engineering significance to provide early warning for coal mine power disasters and reduce disaster accidents.In this paper,laboratory tests and theoretical analysis methods were used to analyze the mechanical properties and parameters of soft coal rock by using non-contact whole-field strain measurement system and acoustic emission testing system to study the mechanism of unstable fracture of soft coal rock,combined with rock mechanics,Fracture mechanics,damage mechanics,construction of soft coal rock damage model.Using the physical similarity simulation method,the uniaxial compression experiment was performed on the self-made soft briquette.The variation trend and numerical value of the compression curve of the coal sample clearly indicate the heterogeneity of the coal in structure,the stress strain of the self-made briquette and the raw coal.The curve has a similar trend of change,and its plastic deformation is larger.Non-contact full-field strain measurement system is used to obtain the deformation images of coal and rock surface,and the strain characteristics of different types of coal rock are analyzed.In the uniaxial compression process,the initial loading stages are all destroyed along the axial loading direction,but with the As the loading progresses,because there is no confining pressure,the coal sample gradually becomes tensile failure,and the tensile stress acts as the main destructive factor in the later period;Acoustic emission signals during the coal rock fracture process are collected to analyze the acoustic emission signals and the coal-rock fracture process.Coupling relationship,the results show that the stable growth stage of acoustic emission signals is a sign of coal rock fracture instability.In the early period of uniaxial stress loading of soft rock,the deformation of the main body is basically along the axial loading direction.After the coal rock is compacted,the transverse tensile stress and the axial compressive stress are deflected under the action of shear stress.Under the action,the stress concentration at the crack tip occurs,and the cracks"shear" the tensile fracture along the axial direction.When a large number of "shearing"tensile strains are generated,they coalesce with each other,eventually leading to the overall instability of the soft coal rock;The damage model based on acoustic emission parameters and the theoretical damage model based on the number of speckles proposed by the basic theory of mechanics were compared with the experimental data.Both damage models can describe the damage conditions of coal samples.