Simulation Of Coal And Gas Outburst Process Based On ABAQUS

Coal and gas outburst is a highly complex phenomenon of mine dynamic damage,which has a very strong destructiveness and suddenness,which greatly restricting the healthy development of China's coal industry.In this paper,the problem of coal and gas outburst which is difficult to calculate by finite element software is studied.The pre-processing module of ABAQUS is redeveloped by Python language.The coal mesh is re-divided by Python script program,and the zero-thickness bonding unit is inserted.Based on the principle of effective stress and the friction contact of ABAQUS based on Mohr-Coulomb criterion,the simulation of the influence of gas pressure on coal body is realized.The generation and expansion of coal fracture and the outburst process of coal body are simulated by using the cohesive unit.The simulation results show that: 1.The in-situ stress increases the strength of the coal body,but at the same time it will cause stress concentration,which will cause the damage of the coal body near the entrance of the cave.The application of in-situ stress increases the effective stress of coal body.According to Mohr-Coulomb criterion,the shear strength of coal body is strengthened,and the tensile failure will not occur.However,at the entrance of the tunnel,stress concentration occurs due to uneven distribution of stress,and a large number of coal bodies break up and protrude at the entrance.The breaking and outburst of the external coal body results in the decrease of the effective stress of the internal coal body,the decrease of the tensile strength and the shear strength,and the failure of the internal coal body begins to occur along with the phenomenon of stress concentration.2.Gas pressure reduces the strength of coal body and causes large area cracks in coal body.Gas pressure reduces the effective stress of coal body,which makes the tensile strength and shear strength of coal body decrease greatly.The stress concentration at the entrance of the cave due to in-situ stress is more obvious than that without gas pressure with the decrease of coal strength.Inside the coal body,because the increase of effective stress caused by in-situ stress is offset by gas pressure,the structural strength of the coal body is more vulnerable than that without gas pressure.3.When gas pressure and ground stress change,the number and speed of coal outburst increase correspondingly,except for the degree of coal fragmentation.Causes include: greater pressure when coal outburst;higher degree of coal fragmentation,smaller coal particles,which is easier to produce high acceleration;less energy consumption when coal tensile shear failure.4.Coal and gas outburst is the result of combined action of in-situ stress and gas pressure.The in-situ stress makes the shear strength of coal body increase,but the stress concentration at the entrance of the cave leads to the destruction and fragmentation of the coal body,which is an important external cause.Gas pressure decreases the shear strength and tensile strength of coal body,resulting in larger cracks in the whole coal body,which is the main internal cause.In this paper,the constitutive relationship of coal body is perfectly integrated into the coal and gas outburst model in ABAQUS.It is necessary to establish coal material in ABAQUS which meets the maximum tensile stress theory,Mohr-Coulomb criterion and effective force principle.And the in-situ stress and gas pressure can be applied intuitively and accurately.The actual simulation results conform to the experimental law,which proves that the finite element secondary development technology can well calculate the process of coal and gas outburst,and also provides a reference for the application of Python secondary development in other fields.