Controlling close boundary of a technogenic placer through changes in technological parameters of washery refuse storage

Purpose is to assess the potential to control boundaries of a technogenic placer through changes in the parameters of washery refuse storage process taking into consideration both size and density of particles of each fraction of the granulometric composition. Methods. The research has applied approaches developed by V.A. Melentiev and M.S. Poliakov Institute of Geotechnical Mechanics of the National Academy of Sciences of Ukraine relying upon the condition of a critical flow origination. Problems to control close boundary of a technogenic placer have been considered in the process of hydraulic washery refuse storing in artificial tailing ponds at the expense of changes in technological factors involving characteristics of dry fraction particles of the hydraulic fluid. Findings. Limitations have been obtained in the form of intervals of changes in technological influence coefficient values; relative velocity of a hydraulic liquid delivery; relative beach slope; and concentration of the hydraulic liquid flowing to the storage. It has been demonstrated that average beach slope is limited by the particle friction coefficient of the fraction on the beach surface; the abovementioned makes it possible to vary the inwash parameter value from 1.56 to 0.22. It has been identified that in the context of the calculations performed using engineering precision dependence of the inwash parameter upon the coefficient number in Pavlovskyi formula may be ignored since relative error of average value of the parameter use is not more than 1%; hence, its average value depending upon a relative beach slope can be approximated by a decreasing linear function.. Originality. For the first time, formulas have been proposed to identify the boundaries of intervals of changes in a set of technological parameters of storing process depending upon the required value of a close boundary of the technogenic placer. The abovementioned helps assess both concentration and velocity of hydraulic liquid getting to the inwash beaches; the beach slope; and particle parameters of solid fraction of the stored washery refuse providing the wanted distance from inner slope of a flood wall to a close boundary of the technogenic placer. Practical implications. Using the research findings, it becomes possible to control geometry of technogenic placers formed in artificial washery refuse dams in the process of its hydraulic storing. Moreover, it helps avoid location of a flood wall of following levels above technogenic placers of lower inwash formations; construct covering between technogenic placers at two neighbouring levels; achieve separation of the technogenic placer from the fractions containing no valuable components while arranging them within different beach areas, and move closer to selective mining of useful mineral.