Numerical Simulation Of Failure Model Of Coal Rock Under Impact Load

China’s coal reserves are abundant,but because of its coal-forming characteristics and production processes(including fully mechanized coal mining,machine transportation,and transshipment,ect.)it is broken and the lump rate is low,when the raw coal is delivered to the users,Which seriously restricts the use value of coal.And in the process of coal mining,dynamic disasters such as coal and gas outbursts are often accompanied,which seriously threatens the safety of coal mines and the lives of people.Coal rock is not only the object of mining,but also the most direct recipient of dynamic disasters such as rockburst.So whether it is to increase the coal forming rate,or from the perspective of the the management of coal mine power disasters,it is all of great practical significance to study the dynamic mechanical properties of coal rock under dynamic loading.Based on the theoretical basis of computational dynamics,this paper takes the coal rock of 13-1 coal seam in Panxie coal mine as the research object.Studies the dynamic response and failure mode of coal rock under impact load,and conducts numerical simulation studies of the coal rock under complex stress state.The main work are as follows:1)The strain rate effect and failure mode of coal rock under different impact velocities were studied by means of a Φ75mm Hopkinson pressure bar(SHPB)experimental device equipped with high-speed camera.And the process of crack generation and propagation was analyzed from a mesoscopic point of view.2)The process of realizing the impact problem by numerical method was introduced from the aspects of geometric nonlinearity,contact nonlinearity(boundary condition)and material nonlinearity.And take the impact of two elastic rod as an example to verify the reliability of the LS-DYNA program and the accuracy of the solution.3)The HJC model in the LS-DYNA software is described in detail.Through the static compression experiments,tensile tests,Hopkinson pressure bar experiments,combined with the literature data of triaxial tests and Hugoniot experiments of coal rock,The values of the coal rock HJC constitutive model parameters were determined.The HJC constitutive model was extended to coal rock materials,and the sensitivity of key parameters was studied..the results show that the model can reflect the strain rateeffect and strain softening property of coal rock under impact load to a certain extent.It can basically reflect the mechanical behavior of coal and rock under the impact load,which can be used as a reference for engineering design and analysis.4)The SHPB experimental numerical model for coal rock was established to verify the uniformity of the stress of the test piece.The dynamic stress-strain curve and failure process were compared,and the process of crack generation and propagation was analyzed from the perspective of energy dissipation.5)The SHPB experimental numerical model for coal rock was established to verify the uniformity of the stress of the test piece.The dynamic stress-strain curve and failure process were compared,and the process of crack generation and propagation was analyzed from the perspective of energy dissipation.6)The process and necessary conditions for the secondary development of the LS-DYNA material model are introduced.As an example,the isotropically-strengthened bilinear elasto-plastic material model is used to illustrate the process of the correctness of secondary development.and gave some suggestions for the secondary development of general material model...