The research aim is establishment of effective parameters for mining of flooded bench by a hydro-mechanized complex with dumping of enclosing rocks in a sludge pond of pit residual space. The established research results make it possible to choose the effective width of the dredger mining cut at the hydromechanical method, taking into account the volume of the excavation and dump pipeline movements. Two technological schemes for the formation of a sludge pond in the pit residual space are proposed, they differ in the direction of the sludge pond movement relatively to the pit front. The established dependence of the number of movements of the sludge pond pipeline on the width of the dump pass allows to choose its effective value, taking into account the number of discharge pipes. Based on the dependence of the average monthly excavation volume and the number of movements of sludge pond pipeline on the width of cut face, the optimal number of discharge pipes is established. The research results allow establishing the effective dredger width of the sludge pond and the number of discharge pipes provided that a transverse or longitudinal pass at the internal sludge pond formation is applied during the mining.

One of the crucial aspects of reducing air consumption when conveying particles with an airlift pump is to know the factors that affect the process of particle motion at an initial velocity of zero. To determine the influence of submergence ratio and physical properties of particles (such as size, shape, and mass) on the onset of vertical particle motion, the airlift pump was taken as the research object, and spherical glass together with irregular shaped coal were used as experimental test particles. The results show that unlike the water-solid environment, the start of particle motion in the water-air mixture does not always occur at a certain value of superficial water velocity and this value also increases with increasing submergence level. Among the parameters considered, the role of submergence ratio is much more effective than the dimensions and the shape of the particle, because by increasing submergence from 0.3 to 0.8, it is possible to reduce air consumption by up to 8 times. Based on this study the corresponding theoretical model derived by Fujimoto et al. is optimized, wherein the overall agreement between the modified theory and present experimental data is particularly good. Contrary to Fujimoto, the minimum superficial water velocity for lifting solids in the air-water mixture is not always smaller than water ambient which indicates on optimum submergence ratio higher than 0.7. Finally, a new criterion was introduced to describe the moment of onset of the particle motion as a function of the superficial fluid velocity ratio for each submergence value.