Over a period of about 20 years a team at the Institute of Mining, Siberian Branch, Academy of Sciences of the USSR, enjoying the effective cooperation of the engineering staff of the Mining Board and mines of the Kuznetsk Metallurgical Group of the Ministry of Ferrous Metallurgy of the USSR. has been working to improve operations in mines. The goal is the creation of the mining technology of the future.The block-pillar systems used for working thick ore deposits have a number of shortcomings: the block is worked stagewise(firstly the reserves in the room s are worked, then the pillars and the ore blocks); the operating rate of the block is low; preparation of the blocks for mining-out work is very laborious; spontaneous caving of the pillars and blocks of untouched ore is frequent during extraction of the rooms, which makes the work more dangerous; the pillars and ore blocks are caved by mass blasting of concentrated mine charges of weight 250-400 tons, which leads w damage in neighboring workings, pillars, and ore blocks as well as to a great amount of restorative work; the production costs of the mined ore are relatively high, etc.To remove these shortcomings, a new technology has been created from research dam on the following basis: a) the creation of a continuous front of preparatory, entry, and extraction work; 2) the possibility of opening up and drilling the whole rock mass or the whole ore body; 3) the possibility of using powerful self-advancing equipment for cutting panels and drilling boreholes in them; 4) guaranteed maximal concentration of mining-out work; 5) the possibility of using highly productive mechanized ore discharge by Sibiryachka vibrofeeders; 6) exclusion of cyclic working of the deposit by introducing procedures without cycles; 7) single-stage working of the deposit; 8) mining the ore in a semieonfined medium without removal of the oversized material.The new ore mining procedure is known as the "system of continuous induced block panel caving with vibrodischarge of the ore." The essential feature of the system is that the ore body is divided into levels of height 40-80 m or more, and the levels are divided in• panels, 16-27 m wide or more, the length being equaI to the thickness of the ore bodies. Pillars are not left between the panels, The ore is mined along a continuous front to the strike of the ore bodies.The new system (Fig. 1) includes drivage of raises and cutting workings with the use of deep boreholes; singlestage ore breaking in a semiconfined medium by deep boreholes, located in concentric groups; discharge, transport, and loading of ore by means of vibrofeeders (VDPU-4TM; Sibiryachka) with corresponding shaping of the bottoms of the panels, w hich are cut by a trench.The technology was developed, perfected, and tested at the Tashtagol'mine. It is now being used at the iron mines of Gornaya Shoriya and Khakasiya (Tashtagol', Kaz, Sheregesh, and Abakan), in the Urals. and at Krivoi Rog.The incorporation of the new technology revealed its high efficiency and suitability for w...
UDCIt is well-known that after explosion of charges in contouring blast holes in the rock beyond the contour, a series of cracks is formed and propagated some way from the surface of the working.Cracks in the walls of workings reduce the subsequent resistance of the rocks to loads, and hence reduce the overall stability of the workings.Furthermore, inexact drilling of the mouths of the blast holes and deviations of the holes during drilling from the plane of the contour of the working usually cause overcutting and roughness of the walls and roofs of the workings.It is usually assumed that the size of the zone of crack formation depends on a number of factors, primarily on the charge weight and type and the mechanical properties of the surrounding rocks. For spherical charges the dimensions of the zone are usually considered to depend on the radius of the charge, i.e., the radius of the cavity occupied by explosives of a certain weight. Therefore it is natural to ask how fracture and crack formation will occur when the charges are of elliptical cross section.Yanovskaya et al.[1] investigated the velocity field arising in an infinite medium on explosion of an elliptical charge using a simplified model of the action of the explosion according to the theory of O. E. Vlasov. According to this theory the action of the explosion is instantaneous, and at the moment at which the energy of the explosion gases is transferred to the medium, the latter is regarded as an ideal incompressible liquid. During the explosion, the velocity field of the particles of the medium has a potential which, at all points within the region, satisfies the well-known equation of Laplace.
During the fracture of rocks by shothole and borehole charges, the efficiency of the shock waves increases with the hardness of the rock [ 1].Modem procedures involving the use of shotholes and boreholes do not permit maximum possible utilization of the shock-wave energy, because during the initiation of the charges by electric detonators the detonation front is located at a large angle to the charge axis, and most of the energy of the detonation wave passes into the rock mass; when the shothole (borehole) is packed full of explosives, a considerable part of the explosion energy is expended on overerushing the adjoining rock beds by shear deformations. This shortcoming may be eliminated by using more complex charges.An additional charge ( Fig. 1: 2) with a much higher detonation velocity than the main charge 1 is located along the axis of the latter. Like the main charge, the additional charge is oriented with respect to the hole axis by centering rings 3. The gap between the charge and the walls of the holeis filled with water 4. Initiation of such a charge is effected by a plain detonator 5. When the latter is fired, the detonation of the additional charge will outstrip that of the main charge owing to the discrepancy between their velocities. Figure 2 shows the formation of the detonation front of the main charge without allowing for the effect of the water sheath on the detonation velocity of the boundary layers of explosive. Let us assume that initiation took place at a point 0, downwards along the charge axis. We can then establish the dependence of the propagation of the detonation front of the main charge axis. We can then establish the dependence of the propagation of the detonation front of the main charge with respect to the exposed surface as the function /3 = f(vt, vz), where ~ is the slope of the detonation front towards the charge axis (we will assume that the charge axis is parallel to the exposed surface) and vz and vz are the detonation velocities of the main and supplementary charges, respectively.A time t has elapsed from the beginning of initiation. Disregarding the diameter of the additional charge because it is so small in comparison with that of the main charge, we can evidently represent the detonation front 6 E/:::r!Lii as the surface of a cone with a base diameter AB. From the triangle AOC we determine tan /5 = AO/OC or, denoting AO and OC by vlt and vzt, respectively, we get tan B = vz/vz. Hence L, From an analysis of the operat ion of such a charge and of Eq.(1), we can infer that the slope of the detonation front towards the exposed surface decreases with increasing difference between the detonation velocities of the additional and main charges; if the detonation velocities are equal (which is the case for a uniform charge), t5 is 45*. With a decrease in 8, the normaI component of the detonation pressure on the charge cavity increases. It will be seen from Fig. 2 thatwhere P2 is the nomaal component of the detonation pressure and Pz is the pressure in the detonation wave front of the...
A recent development In the technology of ore mining is block caving using deep boreholes. In block caving systems an important stage is the last operation -discharge of ore from the caved blocks. Its efficiency depends on varlous geological, constructional, technological, and organizational factors.In the new technology the technological block (the system of working with the above factors) is the object of control. Its Input parameters are the geological conditions under whtch the deposit Is worked, the constructional data of the system of working, the technological parameters, the organization of all types of operations In the block, etc.Since the mode of occurrence of the ore bodies varies over the deposit but is constant within a single block, we must solve the problem of managing the technology of underground working separately for each block.The parameters governing the effectiveness of an underground working system are the width of the compensation slots (rooms), the length of a block to the strike, the distance between the ore discharge workings, their crosssectional areas, the blasting parameters and the amount of explosive expended on breaking down ore, the standard fragment size of the ore discharge from the block, and the minimum metal content of the discharge batch at the moment of cessation of recovery of ore from the block.Any changes in these parameters will influence the efficiency of fiae mining undertaking,The result of control of the technology should be a combination of control factors which wfll ensure continuous ore discharge wtth minimum cost of winning and of production of commercial products and which will give high output per man-shfft tn discharge of ore from the blocks and will cut down the numbers of blocks in various stages of development and extraction operations.Below we give the main mathematical relations In an algorithm for controlling the technology of underground working systems with block caving. Control of Movement of Caved Ore in the Worked-Out AreaFree flow of ore from a block Is governed by the area of the block, the loosening and fragmentation quality of the ore, and the cross sectton of the discharge workings. The problem of controlling the movement of caved ore in the worked-out area Involves such Important factors as the width of the compensation slots (rooms), on which depends the degree of loosening of the ore, the blasting parameters which determine the fragment size of the brokendown ore, and the necessary cross section of the discharge workings.With uniform discharge sequence the minimum permissible coefficient of loosening (bulk expansion) of the ore in the block for which Its movement in the caved mass wtll occur without hanging and arch formation will be given by the formula ~mt. = ~e~ 1,77--0.0264-Mo+0,00026.MoL Institute of Mining, Siberian Branch, Academy of Sciences of the USSR, Novostblrsk.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.