Choice and substantiation of stable crown shapes in deep-level iron ore mining

Abstract

The aim of the paper is to select and substantiate stable shapes of crown pillars through determining regularities of rock pressure impacts on their stability depending on the crown shapes, mining depths and iron ore hardness.Methods. Stress and strain calculations are performed by the ANSYS 16.0 finite element analysis. Triangulation of the 3D model with a 2 m side is conducted to build stress and strain diagrams. In accordance with the conditions of the experiment, the models were created for horizontal, tent, arched and inclined stope crowns with the dip varying within a wide range. The assumed values of rock pressure on the ore massif conform to mining conditions of the Kryvyi Rih basin deposits at the depths of 1200 to 1700 m. Findings.The obtained values of maximum stresses in stope crowns were calculated in respect to mining depth, rock pressure, crown dip, iron ore hardness and relative curvature radius of the arched crowns. It was determined that vertical and inclined compensating rooms should be used in mining rich iron ores at great depths by sublevel caving systems. In case of the room-and-pillar systems used in mining rich iron ores at great depths, a key requirement is to apply tent and arched crowns which provide maximum stability under high rock pressure.Originality. The research proves that the integrated index of maximum stresses in crown pillars varies from -10 to +32 MPa at depths of over 1200 m and is in polynomial and logarithmic dependence on physical and mechanical properties of the ore mass. It also depends on the crown geometry and, in case of the arched crown, acquires minimal values allowing for stable crown pillar exposures at depths reaching 2000 m. Practical implications.The research results allowed to compile the methodological manual "Choice and substantiation of stable crown shapes in deep-level iron ore mining" for the underground mines of the PJSC "Sukha Balka" and "Rodina" mine of the PJSC "Kryvbaszalizrudkom".

Mining of rich iron ore deposits of complex structure under the conditions of rock pressure development

“…It should be noted at the same time that the conditions of the chamber stability are not determined. In the work [60], the author states that when constructing parabolic-shaped stope chambers, the chamber stability and its volume increases ( Fig. 1).…”

Justification of safe underground development of mountain deposits of complex structure by geophysical methods

“…For elastic-plastic properties of rocks, control of the stress-strain state of a rock mass in the process of conducting and developing mining operations (geomechanical and, as an integral part, seismic monitoring). To ensure the stability of mine workings and prevent the dynamic manifestation of rock pressure, forecasting various sections of the rock mass and ores according to the degree of rock burst hazard and prevention of the dynamic manifestation of rock pressure [22,23]. Geomechanical monitoring of the rock mass and pillars of various purposes is carried out by means of sound and mine surveying instruments, string strain gauges, depth and ground benchmarks.…”

Enhancement of the technology of mining steep ore bodies applying the “floating” crown

“…Ore bodies of Kryvyi Rih iron ore deposit (Ukraine) house over 30.2 Bt of ferruginous quartzite with iron content of 24-65% [1][2][3][4]. These ore bodies are mined applying surface and underground methods.…”