Energy Accumulation and Dissipation of Coal with Preopening under Uniaxial Loading

Energy accumulation and dissipation play an important role during the entire process of rock failure. Some flaws, such as preexisting holes, will influence energy accumulation and dissipation. In order to investigate the energy evolution of coal specimen with preexisting holes under uniaxial compression through numerical approaches, the particle simulation method was used in numerical simulations. In this paper, the energy evolution of coal specimen was theoretically analyzed, and the influence of different hole arrangement, such as diameter, spacing, angle, and number, on the evolution characteristics of energy was also discussed. At the same time, the arrangement of the artificial boreholes for preventing the rockburst was explored. The results show that, compared with the intact coal specimen, the change of diameter, spacing, angle, and the number of holes weakened the coal specimen’s capacity to store energy and release strain energy. When the diameter, the vertical distance, and relative angle of preexisting holes were 15 mm, 10∼15 mm, and 60°, respectively, the energy storage limit reached optimal value. For arrangement of the artificial boreholes, the diameter, spacing, and angle can be designed on the basis of those optimal values. This study has a guiding significance in designing the arrangement of the artificial boreholes for mitigation of rockburst.

Numerical Simulation of 2-D Solitary Wave Run-Up over Various Slopes Using a Particle-Based Method

The present paper covers the numerical prediction of the propagation and run-up of a solitary wave over non-flat seabed with various slope angles using a refined MPS (moving particle simulation) method. In the refined method, the corrected gradient model, new staggered divergence-free model, moving-particle wall boundary treatment, and the sub-particle scale turbulence model are applied to obtain more stable and precise results. The simulation results by the developed method are compared with experimental results, and both results were in good agreement. Especially, it can be seen that the complicated and fully-nonlinear behavior of the free-surface motion during the turbulent processes of build-up, break-down, and overturning of the waves are well reproduced by the developed method.

Peculiar properties of the electron beam dynamics simulation by particle-particle methods taking into account delay effects

An analysis of the plane influence separating the interaction space from the electron beam-forming region is made by the particle-particle simulation method with the delay effect. During the simulation, it was shown that the boundary conditions on the surface have a significant effect on the electron beam dynamics in a longitudinal magnetic field and affect the time of formation of the virtual cathode and the particle velocity in the interaction space.