The use of controlled bench caving to work soft rocks is fundamentally new and little studied.The research at various institutes has not yet been published in general form, and therefore the book under review is of interest to a wide circle of specialists. It features a combined approach to the problem, beginning with the theoretical foundations of the process and of methods of caving, and ending wLth technologies and machines for using the new technique.The book consists of seven chapters. Chapter i gives a survey of the literature on the theory of controlled bench caving, gives the scientific-technical principles on which the new method of working is based, and demonstrates its economic efficiency; it also defines the problems of research in controlled bench caving, chapter 2 gives a theoretical analysis of the process of controlled bench caving. It discusses the mechanics of the caving process and suggests methods of calculating the parameters of the caved benches, allowing for the mechanical properties of the constituent rocks. A drawback of this chapter is that it does not make a comparative assessment of the methods of calculation based on the adoption of plane and curved caving surfaces. In addition, it does not consider determination of the bench caving parameters in terms of the three-dimensional problem, and this reduces our confidence in the equations found. Excessive attention is paid to deriving the value of the critical temporarily stable height of a vertical exposure (w 4).Chapter 3 ueats the model method and gives results of research on the caving process based on equivalent materials and natural rocks, for both plane and three-dimensional models. The suggested model-making method, the model rolling technology, and the test rigs and equipment are simple and original, and can be recommended for wide use in modeling shear processes in benches composed of soft rocks. The results of the investigation with models are undoubtedly of scientific and practical interest. However, the relations deduced need to be made more accurate by means of experiments in the field.Chapters 4 and 5 give the results of research on the states of stress in benches, performed with models of equivalent and optically active materials. These chapters demonstrate the wide possibilities of these model methods for solving problems of stability and shear of benches, in particular for determining the region of maximum stress concentrations, the positions of weakening cuts and the character of the proposed shear surface. This is the first time that such research has been applied to caving of soils, and the results are of interest for further work in this field.Chapter 6 gives the results of research on the energy consumption of excavation of caved rocks. It is shown that the scooping force for loosened soil isonehalfto one third of that inthe untouchedrock. In this chapter an important place is occupied by an exposition of the results of research on how shovel volume influences the energy consumption of the scooping process; in our op...
The Institute of Geoteclmical Mechanics of the Academy of Sciences of the Ukrainian SSR, together with the Northern Mining-Processing Combine of the Ministry of Ferrous Metallurgy of the Ukrainian SSR, has developed a fundamentally new continuous excavator for working blasted rock [1,2] in the continuous technology of mining in open iron-ore mines in the Krivbass.To create a pilot model of this fundamentally new machine with a productivity of 1000-1400 mS/h for compact rock, it is necessary to solve a number of problems, many of which can only be solved experimentally if we are to achieve the necessary reliability.For this reason the excavator was designed in stages. First Stage: Theoretical investigation of the kinematics of the equipment and the operational process.Second Stage: Experimental investigation of operational processes on a model in the laboratory.Third Stage: Creation of experimental model of excavator on the basis of a one-bucket machine in order to investigate the operational processes, constructional elements, and technology of work in an actual face.Fourth Stage: Construction, thorough testing, and investigation of a pilot model of the excavator. In this article we will describe the second stage of the work.The laboratory investigations involve a model of the machine, the face, and the working process: therefore to obtain reliable data the most important problem is to determine the scales of the model, after which, according to the aim of the experiment, the actual design of the model is produced. In order to get a quantitative picture of the operational process as well as a qualitative one, it is necessary to select the principal determining parameters, to compile similarity criteria, and to find the modeling scale.The principal determining parameters of the process of scooping up blasted rock are as follows: 1, the characteristic linear dimension of the system under investigation; V, the linear velocity; P, the force (of scooping, thrust, or gravity); 7, the density of the rock; c, its cohesion; f, the coefficient of internal friction; fI, the coefficient of external friction (on metal); ~, the angle of repose; g, the acceleration due to grapvity; t, the time; and Kp, the coefficient of volume increase. We will regard the blasted rock as a close body in which we can, with fair accuracy, neglect cohesion [3].Thus we have 10 determining parameters with three independent quantities [, 7, and t, from which, according to the It-theorem, we can compile seven independent criteria of similarity [4]:Because the problem has three degrees of freedom (three independent parameters), we choose three main model scales, K~= 10 (for notation see below), K_ = 1 (since the model is made in the same conditions as the prototype process), and Kit =_ (because the model is ~ade of the same materials as the prototype). On this basis we calculated the remaining scales of the model (Table 1) [3].
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