period is reduced accordingly, as compared with similar parameters of vibration exciters working in a nonresonance mode.The moments of inertia incerase in proportion to the number of working pairs, with the proportional reduction of the maximum oscillation angles of pistons.An, external dissipative force reduces the effect of energy accumulation. The kinetic energy accumulated by the pistons after a certain number of oscillation cycles is transmitted to the body after reaching a certain limiting amplitude (according to the problem statement) at which the pistons strike against the body.Since the rigidity of the torsion shaft is not regulated during the course of the operation, the periodicity of collisions is constant.The asymmetric operation of the vibration exciter is based on an asymmetry of the piston oscillation angles and angular velocities.In the half-cycles, the pistons have different angular velocities, and each cycle is accompanied by a piston collision with the body in one of the directions.The vibration exciters with an elastic connection between the body and the piston create time-variable oscillation amplitudes and pulse torques: by modifying the rigidity of the torsion shaft during the course of operation, these parameters can be regulated. The vibration exciters with time-variable'vibration and shock parameters open a new potential for intensification of industrial processes.The accumulated energy of vibration exciters operating in a resonance mode, depending on the design, can be transferred partially or fully to the object treated by vibration in various industrial operations. where U is the number of fires per level and n is the serial number of the level.For example, in mines using the shield system, the number of fires per million tons of excavated coal is 1.35 on the first level and 2.35 on the third level.The incerase of the fire hazard with depth is associated with underworking and the spread of the fires that were previously considered extinguished on higher levels. These developments can be presented by using various systems of mining with a reliable insulation of horizons.Institute of Mining, Siberian Branch, Academy of Sciences of the USSR, Novosibirsk.