Argumentation for critical parameters and operating modes in the process of underwater mining of placers

¹ University of York, YO10 5DD, York, United Kingdom
² Institute of Geotechnical Mechanics named by N. Poljakov of National Academy of Sciences of Ukraine, 49005, Dnipro, Simferopolska Str., 2a, Ukraine
³ Ukrainian State University of Chemical Technology, Haharina Ave., 8, Dnipro, 49600, Ukraine
⁴ Oles Honchar Dnipro National University, 49000, Dnipro, Haharina Ave., 72, Ukraine

^* Corresponding author: medvedevaolga1702@gmail.com

Abstract

The purpose of the article is to study the connection between the parameters of the formation of the suction funnel, such as the scattering speed and concentration of the suction mixture, and the concentration of the slurry in the suction pipe, which provides supercritical flow conditions. This connection is considered in terms of the most common process of underwater mining of placers for the open mining technology by suction dredger. The importance of the research is conditioned by the well-known but not yet thoroughly studied phenomenon of a decrease in the performance of the dredger pump on solid material without breaking the vacuum, which in most cases leads to a hydraulic shock in the pressure line. It is argued that the cause of this occurrence is the onset of a critical flow regime in the suction pipe due to inconsistency of the parameters of the hydrotransport modes and suction funnel formation. A combined analysis of the known dependences for the critical rate of hydro transportation in an inclined pipeline and for the geometric parameters of the suction funnel made it possible to establish restrictions on the concentration of solid particles on the surface of the erosion funnel.