Temperature,stress,electromagnetic multi-field coupling mechanism of composite coal-rock deformation and fracture

The evolution of various physical fields in coal-rock dynamic disasters is very complicated. Combined with the interdisciplinary theory of damage mechanics and electromagnetic field theory,the coupled mathematical model of multi-physics field,i. e. ,temperature field,stress field and electromagnetic field,of composite coal rock is deduced. By establishing a multi-field simulation model,the variation rules of the three physical fields are numerically analyzed in the process of loading deformation and failure of coal-rock samples and verified by experiments. The simulation results show that the internal stress of coal-rock changes from loading. At the microscopic point of view,the old molecular chain breaks to form a new molecular chain,which releases heat. Meanwhile,the variable-speed movement towards charged particles of the action of regional electric field produces electromagnetic radiation. Macroscopically,the com- pressive strength of coal is weaker than that of rock,and the stress,temperature and electromagnetic field energy of coal are obviously higher than those of rock. The stress and temperature at the tip of crack is the largest,and the mag- netic field energy increases with the increase of simulation time. The magnetic induction intensity rotates counterclock- wise and decays gradually from the inside to the outside. Under the same conditions,the experimental results show that the infrared radiation temperature shows a step-type growth following the growth of stress,and the temperature reaches the highest near the stress peak. In the initial stage of loading,the electromagnetic radiation ( EMR) slowly increases until the stress reaches a peak value,and the electromagnetic radiation suddenly increases to the maximum. After the coal-rock ruptures,the electromagnetic radiation attenuates sharply until it disappears. The experimental and simulation results are consistent. The coupling model of temperature field,stress field and electromagnetic field can be used to study the characteristics of coal and rock under complex conditions,which provides a theoretical basis and new method for dynamic disaster prediction to exploit deep coal-rock.